dnstls_stream_connect_tls() reads the manager-wide dns_over_tls_mode
field directly, so when the global mode was 'no' or 'opportunistic' but
a link was configured with strict DNSOverTLS=yes, the DoT connection
was established without SSL_VERIFY_PEER or hostname/IP checks.
Use dns_server_get_dns_over_tls_mode() which honours the per-link
override.