Allow to enable fencing, pass through fencing config

Allow to enable fencing, pass through fencing config

Add two new parameters: EnableFencing and FencingConfig.

FencingConfig is a json with an expected structure documented in the
templates. It gets passed further to puppet-tripleo, which configures
the fencing devices.

Fencing is configured and enabled in the last step after all pacemaker
resources and constraints have been created, which should be a more
stable approach than the other way round.

Change-Id: Ifd432bfd2443b6d13e7efa006d4120bb0eaa2554
Depends-On: I819fc8c126ec47cd207c59b3dcf92ff699649c5a
Depends-On: I8b7adff6f05f864115071c51810b41efad887584