BUG/MEDIUM: ssl: Don't store the ALPN for check connections

BUG/MEDIUM: ssl: Don't store the ALPN for check connections

When establishing check connections, do not store the negociated ALPN
into the server's path_param if the connection is a check connection, as
it may use different SSL parameters than the regular connections. To do
so, only store them if the CO_FL_SSL_NO_CACHED_INFO is not set.
Otherwise, the check ALPN may be stored, and the wrong mux can be used
for regular connections, which will end up generating 502s.

This should fix Github issue #3207

This should be backported to 3.3.