Gallery2: Remove wait when notify dirty

When notify Dirty from photo data adapter, where is a operation of
waiting, but this Object.wait is locked by ReloadTask.

Remove the wait when notify dirty, which notify all right away. And
do the delete operation after last picture's deletion is done.

Change-Id: I3c322c8d01944d1e41d784346da930b907efdb1c
CRs-Fixed: 808799