Add Blackbox monitoring for backend endpoints

[Alex-Welsh]

Adding backend blackbox endpoint monitoring.

Some service do not support TLS at all (e.g. Blazar)
Some services do support TLS, and they have a globally-scoped variable (e.g. Neutron, neutron_enable_tls_backend)
Some services do support TLS, but have locally scoped variables, so must use the generic kolla_enable_tls_backend (e.g. Nova)

This is a precursor to proper support in Kolla-Ansible, which I'm planning on doing with file-based service discovery

[Alex-Welsh]

For context, this has been tested in a Multinode.

Confirmed working:

• barbican
• cinder
• designate
• glance
• heat
• heat_cfn
• horizon
• magnum
• neutron
• nova
• octavia
• placement

Untested (not deployed by multinode):

• blazar
• gnocchi
• manila
• ironic
• ironic inspector
• swift

Example templated content:

targets:
    - cinder_backend_rockyovnfqdncontroller01:os_endpoint:https://192.168.37.3:8776
    - cinder_backend_rockyovnfqdncontroller02:os_endpoint:https://192.168.37.4:8776
    - cinder_backend_rockyovnfqdncontroller03:os_endpoint:https://192.168.37.5:8776
    - designate_backend_rockyovnfqdncontroller01:os_endpoint:http://192.168.37.3:9001
    - designate_backend_rockyovnfqdncontroller02:os_endpoint:http://192.168.37.4:9001
    - designate_backend_rockyovnfqdncontroller03:os_endpoint:http://192.168.37.5:9001

[Alex-Welsh]

Updated to include a warning about having separate monitoring nodes

[dougszumski]

Thanks Alex!

[Alex-Welsh]

@dougszumski I've fixed that typo, could you do a quick re-review?

[dougszumski]

Thanks Alex!