include add node functionality for RHEL 7

[radez]

There's not a capability that I can find yet to add a node to a cluster without pcsd running on the node.

Need to add capability to the puppet module to be able to:
a) check that we're running RHEL7+
b) add a node to an existing cluster

[radez]

this can be done in rhel 6 by running this on all nodes
ccs -f /etc/cluster/cluster.conf --addnode

Then after the node has been added on all nodes
On one node:

1. run cman_tool version -S -r