Security attributes must be set when creating a new inode.

We do this in three steps.

- First, get security xattr's name and value by security_operation

- Calculate and reserve the meta data and clusters needed by this security
  xattr before starting transaction

- Finally, we set it before add_entry
Signed-off-by: Tiger Yang <tiger.yang@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>