ceph: make mon client statfs handling more generic

This is being done so that we could reuse the statfs
infrastructure with other requests that return values.

Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: Sage Weil <sage@newdream.net>

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

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

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