qemu-iotests: qcow2: Test growing large refcount table

Actually writing all the content with 512 byte sector size would take
forever, therefore build the image file with a Python script and use
qemu-io for the last write that actually triggers the refcount table
growth.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/tests/qemu-iotests/044.out b/tests/qemu-iotests/044.out
new file mode 100644
index 0000000..7a40071
--- /dev/null
+++ b/tests/qemu-iotests/044.out
@@ -0,0 +1,6 @@
+No errors were found on the image.
+.
+----------------------------------------------------------------------
+Ran 1 tests
+
+OK