For historical reasons the ``haproxy_service_configs`` variable was
a list of nested mappings with only single valid key for the top
level mapping.
There have been no use-cases for extra keys, so this patch simplifies
the code by removing one level of nesting.
Change-Id: I50c17b7020a459ab8a88b004cc8828cac857f1c9
Support for backend options is added to support
arbitrary haproxy options like http-check or tcp-check
Change-Id: I0a5761c14e0bf27ac36d4f27522fbb756bb70950
Related-To: #1681695