ceph: rados pool namespace support

This patch adds codes that decode pool namespace information in
cap message and request reply. Pool namespace is saved in i_layout,
it will be passed to libceph when doing read/write.

Signed-off-by: Yan, Zheng <zyan@redhat.com>

fs/ceph/super.h

@@ -287,7 +287,6 @@ struct ceph_inode_info {
 
 	struct ceph_dir_layout i_dir_layout;
 	struct ceph_file_layout i_layout;
-	size_t i_pool_ns_len;
 	char *i_symlink;
 
 	/* for dirs */