haproxy: Enable/disable health and agent checks (#689)

* Enable/disable health and agent checks

Health and agent checks can cause a disabled service to re-enable
itself.  This adds "health" and "agent" options that will also
enable or disable those checks, matching if the service is to be
enabled/disabled.

* Update plugins/modules/net_tools/haproxy.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update plugins/modules/net_tools/haproxy.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update plugins/modules/net_tools/haproxy.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update plugins/modules/net_tools/haproxy.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* Changes to documentation and changelog.

Changes for the haproxy documentation to resolve issues with
the CI/CD, and adding a changelog fragment.

* Update changelogs/fragments/689-haproxy_agent_and_health.yml

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update changelogs/fragments/689-haproxy_agent_and_health.yml

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update plugins/modules/net_tools/haproxy.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* Add an example of health/agent disable.

* Update plugins/modules/net_tools/haproxy.py

Co-authored-by: Andrew Klychkov <aaklychkov@mail.ru>

Co-authored-by: Felix Fontein <felix@fontein.de>
Co-authored-by: Andrew Klychkov <aaklychkov@mail.ru>

changelogs/fragments/689-haproxy_agent_and_health.yml

@@ -0,0 +1,7 @@
+---
+minor_changes:
+  - haproxy - add options to dis/enable health and agent checks.  When health
+    and agent checks are enabled for a service, a disabled service will
+    re-enable itself automatically.  These options also change the state of
+    the agent checks to match the requested state for the backend
+    (https://github.com/ansible-collections/community.general/issues/684).