BAS: connect gatt service when device is reconnected

As we explictly call BluetoothGatt#disconnect when
the bluetooth device is disconnected, we need to
call BluetoothGatt#connect explictly to make it
reconnect.

Bug:228793905
Tag: #feature

Test: atest BluetoothInstrumentationTests and manually
connect/disconnect LE Audio device repeatedly

Change-Id: Ifd9976329fa9d6734a16f3a3d706e64dc0afda63