Sometimes the vty switching has to be delayed; the vty

to be switched to is saved in sc->delayed_next_scr and
the actual switch is performed later.  It was possible
to get into the endless loop when attempting to switch
to a closed vty (which is not allowed and beep-alerted
when attempted) and when the visual beep was in effect.
This caused sc->delayed_next_scr to never be reset and
endless attempts to switch to a closed vty and endless
visual beeping.  How to repeat:

- boot into single-user
- run "kbdcontrol -b visual"
- quickly press Alt+F2 two times

PR:		kern/68016
X-MFC after:	6.2-RELEASE

sys/dev/syscons/syscons.c

@@ -2176,6 +2176,7 @@ sc_switch_scr(sc_softc_t *sc, u_int next_scr)
 	DPRINTF(5, ("switch delayed\n"));
 	return 0;
     }
+    sc->delayed_next_scr = 0;
 
     s = spltty();
     cur_scp = sc->cur_scp;
@@ -2320,7 +2321,6 @@ sc_switch_scr(sc_softc_t *sc, u_int next_scr)
 
     /* this is the start of vty switching process... */
     ++sc->switch_in_progress;
-    sc->delayed_next_scr = 0;
     sc->old_scp = cur_scp;
     sc->new_scp = sc_get_stat(SC_DEV(sc, next_scr));
     if (sc->new_scp == sc->old_scp) {