Make sure we shutdown the controlconf listeners and connections once

Make sure we shutdown the controlconf listeners and connections once

It was possible that controlconf connections could be shutdown twice
when shutting down the server, because they would receive the
signal (ISC_R_SHUTTINGDOWN result) from netmgr and then the shutdown
procedure would be called second time via controls_shutdown().

Split the shutdown procedure from control_recvmessage(), so we can call
it independently from netmgr callbacks and make sure it will be called
only once.  Do the similar thing for the listeners.