Add fencing agent script as a separated task

Based on nailgun agent, should be installed the same way
To run unit tests use:
rspec ./bin/fencing-agent_spec.rb --color --format documentation

Requirements for tests:
ruby 1.9.3p429 / 1.8.7p371
rspec 2.14.7
---------------------
httpclient (2.3.4.1)
json (1.8.1)
logger (1.2.8)
ohai (6.20.0)
rethtool (0.0.3)

Depends on: https://review.openstack.org/66607
Implements blueprint: fencing-in-nailgun-agent

Change-Id: Iceee47c47d35969f4ff08a0eb5b1e74b12b8b92f
Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
Merge "Add fencing agent script as a separated task"