MEDIUM: server: adding support for check_port in server state

MEDIUM: server: adding support for check_port in server state

We can currently change the check-port using the cli command `set server
check-port` but there is a consistency issue when using server state.
This patch aims to fix this problem but will be also a good preparation
work to get rid of checkport flag, so we are able to know when checkport
was set by config.

I am fully aware this is not making github #953 moving forward, I
however think this might be acceptable while waiting for a proper
solution and resolve consistency problem faced with port settings.

Signed-off-by: William Dauchy <wdauchy@gmail.com>