Fix backups not working when feature_flags table does not exist

Merged Stan Hu requested to merge sh-fix-backup-no-feature-flags-table into master

What does this MR do and why?

Previously this would fail if you attempted to restore the database:

RAILS_ENV=test bundle exec rake db:reset
RAILS_ENV=test bundle exec rake gitlab:backup:db:create
RAILS_ENV=test bundle exec rake gitlab:db:drop_tables
RAILS_ENV=test bundle exec rake gitlab:backup:db:restore

The last step would attempt to read backup_information.yml and fail because the file isn't generated in the gitlab:backup:db:create task. We can disable the reading of that file since it's only needed in the gitlab:backup:create task.

In addition, the third step is optional. Since the feature_flags table does not exist, the feature flag check that happened in the last step would fail.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

Edited by Stan Hu