add indexes for enum columns on job/recipe_set/recipe

These columns were originally implicitly indexed, way back in the day,
when they were INT foreign keys. When they were converted to ENUMs they
should have had an explicit index added.

Change-Id: I6aa4d0ba705dbc2469dfa8a6b4e3b90678d1e697
Merge "add indexes for enum columns on job/recipe_set/recipe" into develop