test_loader: Adapt to latest storage revision_get change
Related to T645
Test Plan
tox (failing until release storage > 0.13.3 and loader.core > 0.9.1
Migrated from D3869 (view on Phabricator)
Staging instance, all changes can be removed at any time
Related to T645
tox (failing until release storage > 0.13.3 and loader.core > 0.9.1
Migrated from D3869 (view on Phabricator)