OPP: Clear Ongoing Notification after transfer complete.

Use Case:
1.Push any file from BM3 dongle to DUT.
2.Accept it on DUT and let the transfer begin.

Error:
Drag down the notification bar and notice that even after
the file is transferred, progress is stuck at 99%.

Root cause:
In Android O clearing of ongoing notification is done on reception of
disconnect from remote. Since BM3 as remote device does not disconnect the
OPP connection, progress bar is stuck at 99%.

Fix:
Clear ongoing notification after file sent successfully without waiting
disconnect request to prevent abnormal UI behaviour.

Test: Issue is not reproducible after stress testing with above change.
Bug: 68832852
Change-Id: Ic514af19de1d554f9299c5daf74fc0d046a67009