qcow2: Keep option in qcow2_invalidate_cache()

Instead of manually building a list of all options from BDRVQcowState
values just reuse the options that were used to open the image.
qcow2_open() won't fully use all of the options in the QDict, but that's
okay.

This fixes all of the driver-specific options in qcow2, except for
lazy-refcounts, which was special cased before.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/qcow2.c

@@ -1178,11 +1178,8 @@ static void qcow2_invalidate_cache(BlockDriverState *bs)
 
     bdrv_invalidate_cache(bs->file);
 
-    options = qdict_new();
-    qdict_put(options, QCOW2_OPT_LAZY_REFCOUNTS,
-              qbool_from_int(s->use_lazy_refcounts));
-
     memset(s, 0, sizeof(BDRVQcowState));
+    options = qdict_clone_shallow(bs->options);
     qcow2_open(bs, options, flags, NULL);
 
     QDECREF(options);