MEDIUM: cli: add check-addr command

MEDIUM: cli: add check-addr command

this patch allows to set server health check address at runtime. In
order to align with `addr` command, also allow to set port optionnaly.
This led to a small refactor in order to use the same function for both
`check-addr` and `check-port` commands.
for `check-port`, we however don't permit the change anymore if checks
are not enabled on the server.

This command becomes more and more useful for people having a consul
like architecture:
- the backend server is located on a container with its own IP
- the health checks are done the consul instance located on the host
  with the host IP

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