Fix event socket reconnections. Refs #11777

SafeConnectToMaster() needlessly checked whether the control socket
was connected before calling ConnectToMasterServer(). This broken
reconnection of the event socket in the event that the control socket
had remained connected.

This doesn't fix the root cause of #11777 but it should eventually
allow the frontend to recover.
(cherry picked from commit fdd8f784a7774ad873992ea9d66e2645ae694c14)