config: drastically improve cman RRP configuration handling
    
    - don't allow configuration of more than 2 rings
    - allow overrided of alternate mcast address and port via
      envars
    - when using broadcast, set different ports on second ring.
      this also required a substantial change in transport handling
    - add support for
      <cman>
       <multicast addr= port= ttl=/>
       <altmulticast addr= port= ttl=/>
      </cman>
    - don't allow overlap of addresses/ports
    - remove redundant port settings in cman
    - change relaxng schema to reflect above changes
    
    Resolves: rhbz#733298
    
    Reviewed-by: Jan Friesse <jfriesse@redhat.com>
    Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>