Test fcgi socket connection

[renatomefi]

Context

Currently we're only testing when sockets are running on localhost:9000, create a test where we connect via socket for instance
How to change FCGI connection is described here: https://github.com/renatomefi/php-fpm-healthcheck#connection-via-socket-or-another-host

Impact

The current docker image would have to be either altered in runtime or build a new one with new php-fpm pool configuration to create a socket