MMS: Create an entry in messaging conversation for WAP PUSH

Messaging application displays the SMS/MMS based on
thread id. If WAP PUSH is present in DB but the actual
retrieval of MMS failed then Messaging app would not
show that message and hence user would never get a chance
to manually download that MMS. Hence it is required that
for every WAP PUSH we create thread id in thread table.

CRs-Fixed: 534457
Change-Id: I7e4b16072a8f2cd5d1424cd8b476ddd98cb9fbeb