clean up exit status.  die is normal.

a good question is why each pid sends a die note to itself.

Reference: /n/atom/patch/applied/telnetexits
Date: Fri Feb 14 04:50:46 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/ip/telnet.c	Fri Feb 14 04:49:22 2014
+++ /sys/src/cmd/ip/telnet.c	Fri Feb 14 04:49:23 2014
@@ -436,6 +436,8 @@
 	}
 	if(strcmp(msg, "hangup") == 0)
 		noted(NCONT);
+	if(strcmp(msg, "die") == 0)
+		exits("");
 	noted(NDFLT);
 }