qemu-img: add compressed clusters to BlockFragInfo

Show how many clusters are compressed.  This can be used to monitor how
many compressed clusters remain and whether to recompress the image.

Suggested-by: Cole Robinson <crobinso@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

tests/qemu-iotests/common.rc

@@ -162,7 +162,7 @@ _cleanup_test_img()
 _check_test_img()
 {
     $QEMU_IMG check "$@" -f $IMGFMT $TEST_IMG 2>&1 | \
-        sed -e "/fragmented$/d" \
+        sed -e '/allocated.*fragmented.*compressed clusters/d' \
             -e 's/qemu-img: This image format does not support checks/No errors were found on the image./' \
             -e '/Image end offset: [0-9]\+/d'
 }