Bluetooth-PBAP: Handle BT sharing stopped exception while BT turn ON

Introduce NULL check and clean up for mConnSocket to handle NULLPOINTER
exception occurs when BT is turned off and turned ON again.

CRs-Fixed: 520397
Change-Id: I3e9f1163a4836a43720741a3f832286a10778dc8
Merge "Bluetooth-PBAP: Handle BT sharing stopped exception while BT turn ON"
Merge remote-tracking branch 'caf/jb_2.5' into cm-10.1