ceph: make sure write caps are registered with auth MDS

Only auth MDS can issue write caps to clients, so don't consider
write caps registered with non-auth MDS as valid.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
ceph: update i_max_size even if inode version does not change

handle following sequence of events:
 - client releases a inode with i_max_size > 0. The release message
   is queued.
 - a 'lookup' request reply from non-auth MDS returns the same inode.
 - client opens the inode in write mode. The version of inode trace
   in 'open' request reply is equal to the cached inode's version.
 - client requests new max size. But the MDS ignores the request
   because the request does not affect client's write range

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