Gallery2: update selected number for database change

mSourceMediaSet will be updated for database changed
But mTotal will not if it is more than zero.

Update mTotal all the time for database changed

CRs-Fixed: 407961

Change-Id: I432b33ba62c04b18c6a1628b6b10dc9b77a72fc1
Merge "Gallery2: update selected number for database change" into du44