mds: share inode max size after MDS recovers

mds: share inode max size after MDS recovers

The MDS may crash after journaling the new max size, but before sending
the new max size to the client. Later when the MDS recovers, the client
re-requests the new max size, but the MDS finds max size unchanged. So
the client waits for the new max size forever. This issue can be avoided
by checking client cap's last_sent, share inode max size if it is zero.
(reconnected cap's last_sent is zero)

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Greg Farnum <greg@inktank.com>