48dea10 fence: Add support for IPv4/IPv6 forcing

Authored and Committed by marx 14 years ago
    fence: Add support for IPv4/IPv6 forcing
    
    Support is added for agents written in Python, which
    uses standard fencing library and connecting
    by SNMP/nss_wrapper or SSH.
    
    Sadly telnet distributed with Fedora/RHEL doesn't
    has support for forcing IPv4/IPv6 connection, so
    it's impossible to implement this feature for agents
    using it.