Remove db_index=True on FSMIntegerField.

It is generally not a good idea to put indexes on fields without serious reasons. Moreover, index should be a good selector, not returning many items. Creating indexes on status fields is the common example of wrong index usage and thus should not be encouraged by the defaults.

I recommend seeing the talks given by Christophe Pettus and Andrew Godwin at DjangoCon during the past years (including the most recent DjangoCon EU 2014). This thing in particular has been pointed out many times as I remember. Dunno where/when exactly it was mentioned, but I recommend all of their talks anyway (these guys truly do know some shlt about databases).