hmp_nbd_server_start: Don't ask for backing image data

'hmp_nbd_server_start' uses only the device name from the data returned
from 'qmp_query_block', thus no backing file information. Use the new
options to suppress asking for the unused parts to save on resources.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-ID: <df71ca72a96d870758695ac57772fcfb87dc8fa0.1770210044.git.pkrempa@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/monitor/block-hmp-cmds.c

@@ -422,7 +422,7 @@ void hmp_nbd_server_start(Monitor *mon, const QDict *qdict)
     /* Then try adding all block devices.  If one fails, close all and
      * exit.
      */
-    block_list = qmp_query_block(false, false, NULL);
+    block_list = qmp_query_block(true, true, NULL);
 
     for (info = block_list; info; info = info->next) {
         if (!info->value->inserted) {