qemu-iotests: make a few more tests generic

Pretend that a non-implemented check is always successful and thus allow
various tests that were qcow2-specific before to be generic.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/tests/qemu-iotests/010 b/tests/qemu-iotests/010
index 4cf969c..a5bee93 100755
--- a/tests/qemu-iotests/010
+++ b/tests/qemu-iotests/010
@@ -40,7 +40,7 @@
 . ./common.rc
 . ./common.filter
 
-_supported_fmt qcow2
+_supported_fmt generic
 _supported_os Linux