ignore the double registration error

allow the substitute of maps from mcexec thread to the syscall channel

the temporary correction of the problem that gethostbyname() after
accept() interruption finishes an error.

executer/kernel/syscall.c

@@ -65,7 +65,14 @@ int register_peer_channel(struct mcctrl_usrdata *ud, void *key, struct mcctrl_ch
 		printk("register_peer_channel(%p,%p,%p):"
 				"already registered. cpu=%d\n",
 				ud, key, ch, cpu);
+		/*
+		 * When mcexec receives a signal,
+		 * it may be finished without doing deregister_peer_channel().
+		 * Therefore a substitute registration is necessary.
+		 */
+#if 0
 		return -EBUSY;
+#endif
 	}
 
 	ud->keys[cpu] = key;