Improve container health check

[florian-h05]

The current health check is "pinging" Kamilio which leads to confusing log messages.
This should be improved.

An option would be to use kamctl monitor or other kamctl commands.
Those however require the mi_fifo module:

loadmodule "mi_fifo.so"

and also see https://kamailio.org/docs/modules/4.4.x/modules/mi_fifo.html.

[florian-h05]

The health check was improved to check the rtpengine and Kamilio service status from supervisorctl.