Merge pull request #1666 from ceph/wip-mds

Wip mds
mds: share max size to client who is allowed for WR cap

WR cap is allowed for the loner client when filelock is in excl->mix
state. MDS should share max size with the loner client in this case.
Otherwise the client may wait for the max size forever.

Fixes: #8092
Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>