Add provision config for 'service_available'.

 * tempest.conf has a new section called 'service_available' that
   indicates the availability for testing of each service
   individually.  Previously only neutron availability was
   configurable.

Change-Id: I28ece895c50adfde6d560922b6f839473913d478
Merge "Add provision config for 'service_available'."
Merge git://github.com/puppetlabs/puppetlabs-openstack