Haproxy to use consul for service discovery

Setup Haproxy to use consul for service discovery.
Earlier it was using etcd.

Note: Couple of occations I have seen that haproxy is getting
configured with blank IP addresses for server check. It seems hiera
was giving array with blank values. This patch should fix that issue
by using consul dns query.
don't all of these need to be real, otherwise, you will create circular references with the loadbalancer itself