Adapt storage.revision_get calls according to latest api change
This also allows the new extra_headers conversion. (current revisions might not have it yet but at some point, they will eventually get migrated to this [1] ;)
That may also fix the master build now (some new code got pushed in the repository since the new storage 0.14.0 release) [2]
Related to T645
Test Plan
tox (failing until release storage > 0.13.3)
Migrated from D3877 (view on Phabricator)