tc-health-client update to v4 API

[jpappa200]

This Improvement request (usability, performance, tech debt, etc.) affects these Traffic Control components:

• Traffic Control Health Client (tc-health-client)

Current behavior:

v3 API will be deprecated soon and needs to updated to v4. The last redesign requires a SIGHUP to reload the config file. we need to add a reload option to the systemd config.

New behavior:

The servers endpoint in the v4 API is more efficient and reduces the amount of failures when contacting the TO API and also eliminates the need for longer timeout settings.
The last redesign requires a SIGHUP to reload the config file when changes are made. adding a reload option to systemd makes it easier for automation such as ansible to reload the configs.

[ocket8888]

v3 API will be deprecated soon...

APIv3 was already deprecated in ATCv7.0.0.