[Bluetooth] reomve 'isConnected' in BluetoothSocket object

BluetoothSocket object doesn't have 'isConnected' property
[Bluetooth] add adapter.sockets.push when calling connectToServiceByUUID API

Socket should be stored in adapter object after creation

concerns TCT test cases :
- BluetoothSocket_onmessage_callback
- BluetoothSocket_readData