Optimise task queue cron by running 50 tasks at a time

Errors while running automated tests (CI server)... unit_tests/cqc__function_sigs [time = 1.04 seconds]... Test cases run: 1/1, Passes: 1, Failures: 163, Exceptions: 0 unit_tests/___api_twitter [time = 0.09 seconds]... Failure (unknown counts) unit_tests/___demonstratr [time = 0.09 seconds]... Failure (unknown counts) unit_tests/___form_to_email [time = 0.15 seconds]... Test cases run: 1/1, Passes: 0, Failures: 1, Exceptions: 0 unit_tests/___search [time = 4.45 seconds]... Test cases run: 1/1, Passes: 397, Failures: 18, Exceptions: 0 unit_tests/___static_caching [time = 1.18 seconds]... Test cases run: 1/1, Passes: 6, Failures: 3, Exceptions: 0 unit_tests/___third_party_code [time = 0.13 seconds]... Test cases run: 1/1, Passes: 556, Failures: 36, Exceptions: 0 unit_tests/__extra_logging [time = 10.25 seconds]... Failure (unknown counts) unit_tests/__rate_limiting [time = 0.56 seconds]... Test cases run: 1/1, Passes: 6, Failures: 2, Exceptions: 0 unit_tests/__resource_closing [time = 0.10 seconds]... Failure (unknown counts) unit_tests/__sitemap [time = 4.74 seconds]... Test cases run: 1/1, Passes: 36873, Failures: 1, Exceptions: 0 unit_tests/_api_cloudinary [time = 0.09 seconds]... Failure (unknown counts) unit_tests/_api_confluence [time = 0.09 seconds]... Failure (unknown counts) unit_tests/_api_currency [time = 0.09 seconds]... Failure (unknown counts) unit_tests/_api_ecommerce_shipping [time = 0.09 seconds]... Failure (unknown counts) unit_tests/_api_ecommerce_tax [time = 0.89 seconds]... Failure (unknown counts) unit_tests/_api_geocoding [time = 0.09 seconds]... Failure (unknown counts) unit_tests/_api_google_safe_browsing [time = 0.09 seconds]... Failure (unknown counts) unit_tests/_api_google_search_console [time = 0.09 seconds]... Failure (unknown counts) unit_tests/_api_ipstack [time = 0.09 seconds]... Failure (unknown counts) unit_tests/_api_moz [time = 0.09 seconds]... Failure (unknown counts) unit_tests/_api_transifex [time = 0.17 seconds]... Failure (unknown counts) unit_tests/_api_translation [time = 0.09 seconds]... Failure (unknown counts) unit_tests/_api_weather [time = 0.09 seconds]... Failure (unknown counts) unit_tests/_cqc_nonbundled [time = 9.84 seconds]... Test cases run: 1/1, Passes: 58, Failures: 29, Exceptions: 0 unit_tests/_eslint [time = 0.09 seconds]... Test cases run: 1/1, Passes: 0, Failures: 1, Exceptions: 0 unit_tests/_protocol_imap [time = 0.09 seconds]... Failure (unknown counts) unit_tests/_tracker_categories [time = 0.28 seconds]... Test cases run: 1/1, Passes: 0, Failures: 113, Exceptions: 0 unit_tests/aaa_modularisation [time = 1.60 seconds]... Test cases run: 1/1, Passes: 0, Failures: 4, Exceptions: 0 unit_tests/adminzone_search [time = 0.22 seconds]... Test cases run: 1/1, Passes: 0, Failures: 1, Exceptions: 0 unit_tests/aws_ses [time = 0.09 seconds]... Test cases run: 1/1, Passes: 1, Failures: 0, Exceptions: 5 unit_tests/basic_code_formatting [time = 3.80 seconds]... Test cases run: 1/1, Passes: 141843, Failures: 3, Exceptions: 0 unit_tests/config [time = 5.00 seconds]... Test cases run: 1/1, Passes: 46342, Failures: 3, Exceptions: 0 unit_tests/cqc_adminzone [time = 2.60 seconds]... Test cases run: 1/1, Passes: 42, Failures: 3, Exceptions: 0 unit_tests/cqc_blocks [time = 0.93 seconds]... Test cases run: 1/1, Passes: 8, Failures: 1, Exceptions: 0 unit_tests/cqc_cms [time = 2.30 seconds]... Test cases run: 1/1, Passes: 5, Failures: 4, Exceptions: 0 unit_tests/cqc_cns [time = 2.30 seconds]... Test cases run: 1/1, Passes: 14, Failures: 4, Exceptions: 0 unit_tests/cqc_forum [time = 0.61 seconds]... Test cases run: 1/1, Passes: 2, Failures: 2, Exceptions: 0 unit_tests/cqc_hooks [time = 10.31 seconds]... Test cases run: 1/1, Passes: 37, Failures: 61, Exceptions: 0 unit_tests/cqc_rest [time = 0.82 seconds]... Test cases run: 1/1, Passes: 9, Failures: 6, Exceptions: 0 unit_tests/cqc_site [time = 2.30 seconds]... Test cases run: 1/1, Passes: 57, Failures: 39, Exceptions: 0 unit_tests/cqc_sources [time = 12.31 seconds]... Test cases run: 1/1, Passes: 140, Failures: 46, Exceptions: 0 unit_tests/dev_environment [time = 0.09 seconds]... Test cases run: 1/1, Passes: 1, Failures: 1, Exceptions: 0 unit_tests/download_indexing [time = 0.10 seconds]... Test cases run: 1/1, Passes: 3, Failures: 1, Exceptions: 0 unit_tests/lang_administrative_split [time = 0.56 seconds]... Test cases run: 1/1, Passes: 23645, Failures: 1, Exceptions: 0 unit_tests/lang_spelling [time = 2.08 seconds]... Test cases run: 1/1, Passes: 0, Failures: 1, Exceptions: 0 unit_tests/persistent_cache [time = 0.14 seconds]... Failure (unknown counts) unit_tests/rootkit_detection [time = 0.09 seconds]... Test cases run: 1/1, Passes: 0, Failures: 1, Exceptions: 0 unit_tests/search [time = 0.55 seconds]... Failure (unknown counts) unit_tests/spreadsheets [time = 0.12 seconds]... Test cases run: 1/1, Passes: 54, Failures: 0, Exceptions: 22 unit_tests/template_no_unused [time = 2.45 seconds]... Test cases run: 1/1, Passes: 907, Failures: 1, Exceptions: 0 unit_tests/template_parameter_consistency [time = 0.88 seconds]... Test cases run: 1/1, Passes: 4272, Failures: 1, Exceptions: 0 unit_tests/tutorial_quality [time = 0.42 seconds]... Test cases run: 1/1, Passes: 3432, Failures: 1, Exceptions: 0 unit_tests/webdav [time = 1.17 seconds]... Test cases run: 1/1, Passes: 2, Failures: 12, Exceptions: 0 unit_tests/zip [time = 0.13 seconds]... Test cases run: 1/1, Passes: 2, Failures: 0, Exceptions: 25