OPP: Reset connection accepted flag

Usecase:
1) Transfer file to remote (10-15 MB)
2) While transfer is ongoing, send file to DUT from another
   remote device. File transfer fails as expected.
3) After Tx completes try to receive file on DUT from any remote.

Observation:
DUT is not accepting the obex connection and all Incoming files are
rejected.

Rootcause:
During Tx ongoing if DUT receives Rx request, DUT waits
upto 20 seconds for Tx to complete and after that rejects
incoming file since OPP service is still busy (with Tx).

Fix:
Reset connection accepted flag to accept new incoming connection
after rejecting incoming connection so that new connection can be
accepted in future.

Test: Checked the above scenario and file could be received
in future iterations when we have incoming Rx during ongoing Tx.

Bug: 36800414
Change-Id: I004ef6ff994bc7c3b3a607053d7bfc9c9b773989