rbd: fix compile error Commit 787e4a85 [block: Add options QDict to bdrv_file_open() prototypes] didn't update rbd.c accordingly. Cc: Kevin Wolf <kwolf@redhat.com> Cc: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Liu Yuan <tailai.ly@taobao.com> Reviewed-by: Stefan Weil <sw@weilnetz.de> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>