qemu-iotests: Filter out vmdk creation options

Cover new image creation options for vmdk, so we can use '-o
zeroed_grain=XXX' and '-o subformat=XXX' to run the tests successfully.
Signed-off-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

tests/qemu-iotests/common.rc

@@ -127,6 +127,8 @@ _make_test_img()
             -e "s# compat='[^']*'##g" \
             -e "s# compat6=\\(on\\|off\\)##g" \
             -e "s# static=\\(on\\|off\\)##g" \
+            -e "s# zeroed_grain=\\(on\\|off\\)##g" \
+            -e "s# subformat='[^']*'##g" \
             -e "s# lazy_refcounts=\\(on\\|off\\)##g"
 
     # Start an NBD server on the image file, which is what we'll be talking to