MFC r249807,249893

  Fix installkernel requiring users/groups defined in CHECK_UIDS
  and CHECK_GIDS to exist since r152680. This is only needed for
  installworld. The documented procedure of running mergemaster -p
  to check for missing users is only needed for installworld, not
  for installkernel. This fixes auditdistd incorrectly being
  required for installkernel.

PR:		misc/174405