Cleanup GATT cache when remote device is disconnected

According to Bluetooth spec, GATT cache should not be persisted between
reconnections for unbonded devices. Bonded devices store the cache on
the disk and will read it on reconnection.

Bug: 33123476
Test: sl4a GattReadTest
Change-Id: If2ca53c7b22a346e7236514ea7b461695c923f74
(cherry picked from commit d19485ec)