[#4837] add index on forum_thread import_id
[#4837] add index on forum_thread import_id

apache/allura,Bitergia/allura,lym/allura-git,Bitergia/allura,heiths/allura,apache/allura,heiths/allura,apache/allura,heiths/allura,Bitergia/allura,apache/allura,lym/allura-git,apache/incubator-allura,heiths/allura,apache/incubator-allura,Bitergia/allura,lym/allura-git,apache/incubator-allura,Bitergia/allura,apache/allura,heiths/allura,lym/allura-git,apache/incubator-allura,lym/allura-git