deposit.loader: Fix committer date appropriately
Thix fixes the loader deposit to use the correct field date sent from the deposit read api.
This adds another test scenario where committer date and author date are different. This is to further check the dates are set correctly in the revision. In the previous test data, the committer date and author were the same so no hash change were detected.
Related to T2368
Test Plan
tox
Migrated from D3039 (view on Phabricator)