* Revert to using rpc for mixed mode AD domains.

* Revert to using rpc for mixed mode AD domains.
  The reason for this are:
  (a) the set_dc_type_and_flags() cannot tell the different
      between connecting to an NT4 domain and an NT4 BDC
      of a mixed mode domain.
  (b) the connection management for the rpc backend only
      provides on named pipe per cli_state.  So it is possible
      to connect to an NT4 BDC for netlogon and an AD mixed mode
      DC for lsarpc.  RPC is the lowest common demonimator here.
  (c) Issue with the sequence number value between the
      highestCommittedUSN LDAP attribute and the seq_num returned
      via RPC.

We will revisit this later, but the changes need to make this
work right now are too broad and risky.