backport of SP3 fixes

to cluster nodes (bnc#802814)
- cluster allows DHCP configuration, but check if IPs are configured
  for it (bnc#811008)
- show error message when cluster config is not correct (bnc#809208)
- ensure cluster options are present in smb.conf during join
  (bnc#809208) and testjoin (bnc#810592)
- 2.24.0