- mdt_obj_create() understands a request which is part of cross-node mkdir()

  recovery and looks for given ino/generation first. if no ino/generation are
  given then it simple recreates new object and returns ino/generation back
  to MDS holding a name. leaked inode is subject to rollback mechanism that
  is to be implemented yet
- when mds_reint_create() is asked to replay cross-node mkdir() it signals
  this to MDS holding dir inode and sends ino/generation couple if possible

NOTE: now cross-node mkdir() survives failure on any MDS node: holding the
      name and holding the inode