Bluetooth: Fix resource leak in OPP (2/3)

This patch handles onPause in DevicePickerFragment class, which
would be called when user presses back button and does not select
any device. This will send intent to class that called
DevicePickerFragment that no device is selected.

CRs-Fixed: 662147, 706665
Change-Id: I3dcf2811b300e44c0f3cb713c1397b5d334e8284