ripd: failure to create a socket shouldn't be a fatal error

The ripd code can handle this error just fine (e.g. reject the
configuration transaction), there's no need to exit when a socket
fails to be created.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>

ripd/ripd.c

@@ -1347,7 +1347,7 @@ int rip_create_socket(void)
 	if (sock < 0) {
 		flog_err_sys(EC_LIB_SOCKET, "Cannot create UDP socket: %s",
 			     safe_strerror(errno));
-		exit(1);
+		return -1;
 	}
 
 	sockopt_broadcast(sock);