[BT] Fix bug: MAP client can not get MessageListing for draft folder

Currently c.getColumnIndex(Mms.PRIORITY) in setPriority method is returning
-1 which is causing c.getInt(-1) to throw a java.lang.IllegalStateException.

The fix is to add the column Mms.PRIORITY in MMS_PROJECTION

Bug 15069197 and 15071221

Change-Id: I9f296415efd5e10970d9f24652cab1022dad5efd
Signed-off-by: Benson Huang <benson.huang@mediatek.com>