Add fence_kdump support for generic clusters
    
    Adds two new options to kdump.conf to be able to configure fence_kdump
    support for generic clusters:
    
      fence_kdump_args <arg(s)>
        - Command line arguments for fence_kdump_send (it can contain all
          valid arguments except hosts to send notification to)
    
      fence_kdump_nodes <node(s)>
        - List of cluster node(s) separated by space to send fence_kdump
          notification to (this option is mandatory to enable fence_kdump)
    
    Generic clusters fence_kdump configuration take precedence over older
    method of fence_kdump configuration for Pacemaker clusters. It means
    that if fence_kdump is configured using above options in kdump.conf, old
    Pacemaker configuration is not used even if it exists.
    
    Bug-Url: https://bugzilla.redhat.com/1078134
    Signed-off-by: Martin Perina <mperina@redhat.com>
    Acked-by: Vivek Goyal <vgoyal@redhat.com>