qemu-iotests: Cleanup test image in test number 007

qemu-iotests number 007 doesn't do test image cleanup. This will affect
those protocols that expect a clean state before every test. Hence
ensure that test image is cleaned up in this test.
Signed-off-by: NBharata B Rao <bharata@linux.vnet.ibm.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/007

@@ -30,7 +30,7 @@ status=1	# failure is the default!
 
 _cleanup()
 {
-#	_cleanup_test_img
+	_cleanup_test_img
 	true
 }
 trap "_cleanup; exit \$status" 0 1 2 3 15