This follows up
https://github.com/wikimedia/phabricator/commit/7c5b5327c8cc4e6bba0f255688164035cefbb4a2#diff-0c81839f27ee178e988b7c8fcfa68bafR20
Also add some sql logic so that it will drop the index and then recreate
it with the extra key.
Also change key_corpus back to corpus as there was no sql updates that
changed the columb to key_corpus from corpus.
Change-Id: I70b40646dc843da0529402d01a2c17db86b05716