mds: fix corner case of pushing inline data

mds: fix corner case of pushing inline data

Following sequence of events can happen.
 - Client releases an inode, queues cap release message.
 - A 'lookup' reply brings the same inode back, but the reply doesn't
   contain inline data because MDS didn't receive the cap release
   message and thought client already has up-to-data inline data.

The fix is trigger a getattr if client finds inline_version is zero.
The getattr mask is set to CEPH_STAT_CAP_INLINE_DATA, so that MDS knows
client does not have inline data.

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