tests: skip raid test on 3.12.0

3.12.0 kernel prevents raid test to be usable,
leaving unremovable devices in table.

This needs to be fixed ASAP, meanwhile disable test to make
test machines at least usable.

test/lib/aux.sh

@@ -689,6 +689,12 @@ target_at_least()
 	  dm-*) modprobe "$1" || true ;;
 	esac
 
+	if test "$1" = dm-raid; then
+		case "$(uname -r)" in
+		  3.12.0*) return 1 ;;
+		esac
+	fi
+
 	local version=$(dmsetup targets 2>/dev/null | grep "${1##dm-} " 2>/dev/null)
 	version=${version##* v}
 	shift

test/shell/lvconvert-raid.sh

@@ -22,10 +22,7 @@ get_image_pvs() {
 ########################################################
 # MAIN
 ########################################################
-if ! aux target_at_least dm-raid 1 2 0; then
-	dmsetup targets | grep raid
-	skip
-fi
+aux target_at_least dm-raid 1 2 0 || skip
 
 # 9 PVs needed for RAID10 testing (3-stripes/2-mirror - replacing 3 devs)
 aux prepare_pvs 9 80