5200 ipf_stack_destroy error messages when halting zones

Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Igor Kozhukhov <ikozhukhov@gmail.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Reviewed by: Darren Reed <darrenr@fastmail.net>
Approved by: Richard Lowe <richlowe@richlowe.net>

usr/src/uts/common/inet/ipf/ip_fil_solaris.c

@@ -143,9 +143,10 @@ ipf_stack_t *ifs;
 	do {								\
 		if (ifs->_f != NULL) {					\
 			if (ifs->_b) {					\
-				ifs->_b = (net_hook_unregister(ifs->_f,	\
-					   _e, ifs->_h) != 0);		\
-				if (!ifs->_b) {				\
+				int tmp = net_hook_unregister(ifs->_f,	\
+					   _e, ifs->_h);		\
+				ifs->_b = (tmp != 0 && tmp != ENXIO);	\
+				if (!ifs->_b && ifs->_h != NULL) {	\
 					hook_free(ifs->_h);		\
 					ifs->_h = NULL;			\
 				}					\