iotests: Fix 067 for compat=0.10

067 works very well with compat=0.10 once you remove format-specific
information from the QMP output.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20171123020832.8165-14-mreitz@redhat.com
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>