click_package/tests/integration/helpers.py: Make tmpdir used for test-internal...

click_package/tests/integration/helpers.py: Make tmpdir used for test-internal click package creation accessible by all.

This is needed if integration tests run as root via autopkgtests.

When run as root, the tempdir gets created as user root, but the tests are faked to be run as user:group daemon:daemon. The relaxed tempdir permissions are required to allow the fake user 'daemon' to enter the tempdir.