libceph: fix safe completion

commit eb845ff13a44477f8a411baedbf11d678b9daf0a upstream.

handle_reply() calls complete_request() only if the first OSD reply
has ONDISK flag.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>