block/gluster: fix QMP to match debug option

block/gluster: fix QMP to match debug option

The QMP definition of BlockdevOptionsGluster:
{ 'struct': 'BlockdevOptionsGluster',
  'data': { 'volume': 'str',
            'path': 'str',
            'server': ['GlusterServer'],
            '*debug-level': 'int',
            '*logfile': 'str' } }

But instead of 'debug-level we have exported 'debug' as the option for choosing
debug level of gluster protocol driver.

This patch fix QMP definition BlockdevOptionsGluster
s/debug-level/debug/

Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Prasanna Kumar Kalever <prasanna.kalever@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>