TelephonyProvider: Improve the performance of deleting Mms.

Triggers "update_threads_on_delete_part" and "mms_words_delete"
run too many times, when delete attachment rows from part
table, it caused Mms application can't deleting lots of MMS
in an acceptable time.

1. Drop the triggers "update_threads_on_insert_part" and
2. Add code instead of trigger's job to avoid unnecessary
operation, when delete a lot of mms.

Change-Id: I151aca0354e157821306ef50d9d3745bdaf4ce99
CRs-Fixed: 786459, 1016740
2 files changed