Do not send requests if socket layer is not established

Change-Id: Id48bab96a1a98e8bb36049d626109a1b0fae7976
gstsctpserversrc: Implement query callback

Change-Id: I2906b669c07a6f5699abf7cdebd0f96f9e0bded1
gstsctpclientsrc: Implement event callback

Change-Id: Id4446e7a64de0e21e0ede28ac25c93c351392407