Don't use non-signal-safe functions (exit(3) in this case) in

signal handlers.  In this case, use _exit(2) instead, following
the call to shutdown(2).

This fixes rare telnetd hangs.

PR:		misc/33672
Submitted by:	Umesh Krishnaswamy <umesh@juniper.net>
MFC after:	1 month

contrib/telnet/telnetd/sys_term.c

@@ -1327,5 +1327,5 @@ cleanup(int sig __unused)
 	(void)chmod(line, 0666);
 	(void)chown(line, 0, 0);
 	(void) shutdown(net, 2);
-	exit(1);
+	_exit(1);
 }

crypto/telnet/telnetd/sys_term.c

@@ -1327,5 +1327,5 @@ cleanup(int sig __unused)
 	(void)chmod(line, 0666);
 	(void)chown(line, 0, 0);
 	(void) shutdown(net, 2);
-	exit(1);
+	_exit(1);
 }

libexec/telnetd/sys_term.c

@@ -1180,5 +1180,5 @@ cleanup(int sig __unused)
 	(void)chmod(line, 0666);
 	(void)chown(line, 0, 0);
 	(void) shutdown(net, 2);
-	exit(1);
+	_exit(1);
 }