cman: add option to init script to prevent joining the fence domain
    
    New sysconfig variable FENCE_JOIN will control whether or not the
    node joins the fence domain. This variable can be set to either
    value "yes" or "no". When FENCE_JOIN is set to "no", the init script
    will not attempt to join the fence domain. Any other value is
    equivalant to "yes", in which case the init script will attempt to
    join the fence domain. (BZ #455598)