iotests: Use -qmp-pretty in 067

067 invokes query-block, resulting in a reference output with really
long lines (which may pose a problem in email patches and always poses a
problem when the output changes, because it is hard to see what has
actually changed). Use -qmp-pretty to mitigate this issue.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/067

@@ -39,7 +39,7 @@ _supported_os Linux
 function do_run_qemu()
 {
     echo Testing: "$@"
-    $QEMU -nographic -qmp stdio -serial none "$@"
+    $QEMU -nographic -qmp-pretty stdio -serial none "$@"
     echo
 }