Fixes a bug in the BluetoothDevice#getIdentityAddress API where it

returns the mAddress field of the device instead of null when the
identity address is not known.

Tag: #feature
Bug: 238353063
Test: atest AdapterServiceTest#testAddressConsolidate
Ignore-AOSP-First: Change needs to land in TM release
Change-Id: I577843c9e2cc279915d0632ff25bde66aa949e94