MEDIUM: ssl/server: No longer store the SNI of cached TLS sessions

MEDIUM: ssl/server: No longer store the SNI of cached TLS sessions

Thanks to the previous patch, "BUG/MEDIUM: ssl: Don't reuse TLS session
if the connection's SNI differs", it is no useless to store the SNI of
cached TLS sessions. This SNI is no longer tested and new connections
reusing a session must have the same SNI.

The main change here is for the ssl_sock_set_servername() function. It is no
longer possible to compare the SNI of the reused session with the one of the
new connection. So, the SNI is always set, with no other processing. Mainly,
the session is not destroyed when SNIs don't match. It means the commit
119a4084bf ("BUG/MEDIUM: ssl: for a handshake when server-side SNI changes")
is implicitly reverted.

It is good to note that it is unclear for me when and why the reused session
should be destroyed. Because I'm unable to reproduce any issue fixed by the
commit above.

This patch could be backported as far as 3.0 with the commit above.