ceph: check inode caps in ceph_d_revalidate

Some inodes in readdir reply may have no caps. Getattr mds request
for these inodes can return -ESTALE. The fix is consider dentry that
links to inode with no caps as invalid. Invalid dentry causes a
lookup request to send to the mds, the MDS will send caps back.

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

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

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

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