Bluetooth-OPP: Check for the pending batch to start next batch

During concurrent inbound and outbound transfer batches if one of
them is finished, then should check for the pending batch to start
next batch. Otherwise, next batch will not start until last
running batch is finished.

CRs-Fixed: 703671
Change-Id: I126c7cba117b379f932d7fb2a3d467e72cf494b1