Certain services are expected to be served by more than one server,
think of git mirrors, zuul workers etc.
While we could define all of them with numbered pattern manually
in the resources.yaml file, this gets unwieldy and boring
if the count is large, repeating on and on the same
server stanzas with just <service_name><$NODE_COUNT>.
This change allows to put a 'node_count' attribute to the server
resource. With it, the role will create as many servers as
'node_count' by numbering the servers as <server_name><$NODE_COUNT>.
e.g.
servers:
- name: logstash-worker.openstack.org
image: ubuntu-trusty
flavor: d1
node_count: 2
That would make the role to create two server instances named
'logstash-worker01.openstack.org' and 'logstash-worker02.openstack.org'
Change-Id: I220a2786efe56187f60f1eed2f32e661e6d3ed3f
205f4d31de