Bluetooth: Null check added before accessing the Adapter service

Null check is being added before accesing the Adapter service's
APIs like createBondNative, cancelBondNative.

CRs-Fixed: 552616
Change-Id: I22acb495f8aa76683dae4bc68376443a67f45b0a
(cherry picked from commit 290a84bc2753ff171b53b768b7a124f35813de6f)
(cherry picked from commit 40b3cb2c511791161c94073c2e8bde6c63e1fd32)
(cherry picked from commit 84421a90559fb368b9d603b6c59c63737a62746f)