Fix Jenkins translation jobs

The jobs nova-propose-translation-update and
nova-upstream-translation-update do not update from
transifex since our po files contain duplicate entries where
obsolete entries duplicate normal entries.

Remove all obsolete entries to fix the jobs.

Change-Id: I7f51922472f12f3a13feb71a6fb344076781d7e9
Closes-Bug: #1299349
Merge "Fix Jenkins translation jobs"