ceph: Reconstruct the func ceph_reserve_caps.

Drop ignored return value.  Fix allocation failure case to not leak.

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Reviewed-by: Sage Weil <sage@inktank.com>

diff --cc fs/ceph/caps.c
Simple merge

diff --cc fs/ceph/super.h
Simple merge