Add bare-centos6 and py3k-precise nodes to hpcloud

* .../templates/nodepool/nodepool.yaml.erb: The bare-centos6 and
py3k-precise nodepool node types are tested and confirmed to work as
intended in hpcloud-az1, az2 and az3.

Change-Id: I110117a199e2eb06b9165fe3e8f8862b570a00ca
Merge "Add bare-centos6 and py3k-precise nodes to hpcloud"