MEDIUM: check: do not auto configure SSL/PROXY for dynamic servers

MEDIUM: check: do not auto configure SSL/PROXY for dynamic servers

For server checks, SSL and PROXY is automatically inherited from the
server settings if no specific check port is specified. Change this
behavior for dynamic servers : explicit "check-ssl"/"check-send-proxy"
are required for them.

Without this change, it is impossible to add a dynamic server with
SSL/PROXY settings and checks without, if the check port is not
explicit. This is because "no-check-ssl"/"no-check-send-proxy" keywords
are not available for dynamic servers.

This change respects the principle that dynamic servers on the CLI
should not reuse the same shortcuts used during the config file parsing.
Mostly because we expect this feature to be manipulated by automated
tools, contrary to the config file which should aim to be the shortest
possible for human readability.

Update the documentation of the "check" keyword to reflect this change.