Add fencing options to quickstack::pacemaker::common

From my testing, fence resources were created for my three vm's:

    # pcs status
    Cluster name: openstack
    Last updated: Fri Mar  7 17:54:57 2014
    Last change: Thu Mar  6 18:20:02 2014 via cibadmin on 192.168.200.30
    Stack: cman
    Current DC: 192.168.200.20 - partition with quorum
    Version: 1.1.10-14.el6_5.2-368c726
    3 Nodes configured
    3 Resources configured
    
    
    Online: [ 192.168.200.10 192.168.200.20 192.168.200.30 ]
    
    Full list of resources:
    
     fence_xvm-c1a3 (stonith:fence_xvm):    Started 192.168.200.20
     fence_xvm-c1a2 (stonith:fence_xvm):    Started 192.168.200.30
     fence_xvm-c1a1 (stonith:fence_xvm):    Started 192.168.200.10

Using quickstack::pacemaker::common parameter values of fencing_type =
fence_xvm, fence_xvm_clu_iface = eth2, and fence_xvm_manage_key_file =
false ( /etc/cluster/fence_xvm.key was copied onto the VM's before
running the puppet agent, though they could be copied after the
stonith resources are created and the fencing resources would still
work).  Taking down the network interfaces on one of the nodes causes
it to be fenced/rebooted.

Also tested fencing_type = 'disabled', which appropriately set the
stonith-enabled property to false and did not install fence_xvm.

Also tested fencing_type = "", which does *not* set stonith-enabled to
false (i.e., do nothing at all with respect to fencing).

Also verified that setting fence_xvm_manage_key_file = true and
fence_xvm_key_file_password = 'somesecretpayload' caused
/etc/cluster/fence_xvm.key to be updated with 'somesecretpayload' .

This work depends on https://github.com/radez/puppet-pacemaker/pull/14