iotests/197: Fix for compat=0.10

Writing zeroes to a qcow2 v2 images without a backing file results in an
unallocated cluster as of 61b30439.  197 has a test for COR-ing a
cluster on an image without a backing file, which means that the data
will be zero, so now on a v2 image that cluster will just stay
unallocated, and so the test fails.  Just force compat=1.1 for that
particular case to enforce the cluster to get allocated.

Fixes: 61b30439Signed-off-by: NMax Reitz <mreitz@redhat.com>
Message-Id: <20200727135237.1096841-1-mreitz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

tests/qemu-iotests/197

@@ -112,7 +112,9 @@ echo
 echo '=== Partial final cluster ==='
 echo
 
-_make_test_img 1024
+# Force compat=1.1, because writing zeroes on a v2 image without a
+# backing file would just result in an unallocated cluster
+_make_test_img -o compat=1.1 1024
 $QEMU_IO -f $IMGFMT -C -c 'read 0 1024' "$TEST_IMG" | _filter_qemu_io
 $QEMU_IO -f $IMGFMT -c map "$TEST_IMG"
 _check_test_img