Skip gnop tests if the corresponding kernel module isn't available.

Reviewed by:	asomers
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D13500

tests/sys/geom/class/nop/nop_test.sh

@@ -36,6 +36,7 @@ diskinfo_head()
 }
 diskinfo_body()
 {
+	load_gnop
 	us=$(alloc_md)
 	atf_check gnop create /dev/${us}
 	md_secsize=$(diskinfo ${us} | cut -wf 2)
@@ -62,6 +63,7 @@ io_head()
 }
 io_body()
 {
+	load_gnop
 	us=$(alloc_md)
 	atf_check gnop create /dev/${us}
 
@@ -87,6 +89,7 @@ size_head()
 }
 size_body()
 {
+	load_gnop
 	us=$(alloc_md)
 	for mediasize in 65536 524288 1048576; do
 		atf_check gnop create -s ${mediasize} /dev/${us}
@@ -111,6 +114,7 @@ stripesize_head()
 }
 stripesize_body()
 {
+	load_gnop
 	us=$(alloc_md)
 	for ss in 512 1024 2048 4096 8192; do
 		for sofs in `seq 0 512 ${ss}`; do
@@ -164,3 +168,10 @@ common_cleanup()
 	fi
 	true
 }
+
+load_gnop()
+{
+	if ! kldstat -q -m g_nop; then
+		geom nop load || atf_skip "could not load module for geom nop"
+	fi
+}