curl: SMTP connection reuse ignores --ssl-reqd / CURLOPT_USE_SSL and reuses a clear-text STARTTLS session on current master

Summary: Current master reintroduces a STARTTLS connection-reuse bug in SMTP. After commit 91dcf4e610 url: urlmatchdestination fix, curl/libcurl can reuse an already-established clear-text smtp:// session for a later logical request that explicitly requires TLS via --ssl-reqd or CURLOPTUSESSL =...