Bluetooth-OPP: Use a volatile variable to denote interrupt status

Sometimes, isInterrupted() can not return true and no
interruptedException throw after uiUpdateThread.interrupt(),
which cause the dead loop in ContentResolverUpdateThread. So
a volatie variable is used instead of isInterrupted() to denote
interrupt status.

CRs-Fixed: 979690

Change-Id: I45ec1c20b5a381ba75aca589c28a0ddd94573d0c