fence/agents: New fencings agents
    
    There are new fencing agents based on a new library. They need a 'pexpect' package.
    If it is possible there is support for both telnet and ssh.
    In this patch there are agents for: APC, BladeCenter, Drac 5, ILo and WTI.
    
    Fence agents that support ssh in 4.7 are iLO, DRAC5, WTI, APC, and BladeCenter