qemu-iotests: add ability to exclude certain protocols from tests

Add the ability for shell script tests to exclude specific
protocols.  This is useful to allow all protocols except ones known to
not support a feature used in the test (e.g. .bdrv_create).
Signed-off-by: NJeff Cody <jcody@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/common.rc

@@ -379,6 +379,18 @@ _supported_proto()
     _notrun "not suitable for this image protocol: $IMGPROTO"
 }
 
+# tests whether $IMGPROTO is specified as an unsupported image protocol for a test
+#
+_unsupported_proto()
+{
+    for f; do
+        if [ "$f" = "$IMGPROTO" ]; then
+            _notrun "not suitable for this image protocol: $IMGPROTO"
+            return
+        fi
+    done
+}
+
 # tests whether the host OS is one of the supported OSes for a test
 #
 _supported_os()