Prevent a double-free

This can occur because prior to this, there is a code path that looks
like this:

    primaryConn = myLocalConn

CloseConnections will subsequently try to free both with PQFinish.
I'm not sure if this is the right fix -- it's more of hack -- without
more information about design intention.

One reasonable alternative would be to have CloseConnections perform
this check itself. As-is I am pretty sure that this fix leaves a
signal-race (when CloseConnections is called, without the check, in
the interrupt handler) unfixed.

Signed-off-by: Dan Farina <drfarina@acm.org>
Signed-off-by: Peter van Hardenberg <pvh@heroku.com>

repmgrd.c

@@ -180,6 +180,10 @@ main(int argc, char **argv)
 		MonitorCheck();
 	}
 
+	/* Prevent a double-free */
+	if (primaryConn == myLocalConn)
+		myLocalConn = NULL;
+
 	/* close the connection to the database and cleanup */
 	CloseConnections();