Add load-balancer manifest and host group

This patch adds the quickstack::load_balancer class which will deploy
haproxy to load-balance the OpenStack API services. This class must be
passed both the public and private virtual IP addresses, as well as a
comma-separated list of backend server addresses and hostnames.
Add mysql_host and qpid_host parameters

This patch allows the addresses for both mysql and qpid servers to set
independently of the controller private IP address. This provides
greater flexibility. For example, if the controller, mysql and qpid
servers had different virtual IP addresses. Note that the default
value will still be the controller private IP address, so unless these
new parameters are overridden there is no change in behavior.
Merge pull request #18 from rohara/devel

Add load-balancer manifest and host group