Add missing indexes back in from 152

Migration 152 lost indexes on upgrade. This was fixed in migration 194
and 212 but one index is still missing on the migrations table.

This patch ensures the indexes are present on downgrade of 152 to be
consistent and also adds the missing index back in with a new migration.

Fixes bug 1208652
bp: db-sync-models-with-migrations
Change-Id: I9f42b3fbe891187382135f8e789f13bb2d35d450
Merge "Add missing indexes back in from 152"