This patch adds loadbalancer-config role
which is "wrapper" around haproxy-config
and proxysql-config role which will be added
in follow-up patches.

Change-Id: I64d41507317081e1860a94b9481a85c8d400797d

Both include_role and import_role expect role's name to be given
via "name" param instead of "role".
This worked but caused errors with ansible-lint.
See: https://review.opendev.org/694779

Change-Id: I388d4ae27111e430d38df1abcb6c6127d90a06e0

Having all services in one giant haproxy file makes altering
configuration for a service both painful and dangerous. Each service
should be configured with a simple set of variables and rendered with a
single unified template.

Available are two new templates:

* haproxy_single_service_listen.cfg.j2: close to the original style, but
only one service per file
* haproxy_single_service_split.cfg.j2: using the newer haproxy syntax
for separated frontend and backend

For now the default will be the single listen block, for ease of
transition.

Change-Id: I6e237438fbc0aa3c89a3c8bd706a53b74e71904b