MMS: First Mms will be deleted when edit second sending Mms

When we edit a sending Mms, this Mms will be draft status.
At this moment, if we edit another sending Mms, the first Mms
will be delete and the second Mms will be a draft message and
in edit status, becase one threadID just have only one draft
message.

Send the first Mms then make the second Mms to edit status.

CRs-Fixed: 410267

Change-Id: Icd55230ca8ab57dd9875762a4364f88dde5bf795