Upgrade from 1.15.1 to 1.15.2.

<ChangeLog>

*) Feature: the $ssl_preread_protocol variable in the

ngx_stream_ssl_preread_module.

*) Feature: now when using the "reset_timedout_connection" directive

nginx will reset connections being closed with the 444 code.

*) Change: a logging level of the "http request", "https proxy request",

"unsupported protocol", and "version too low" SSL errors has been
lowered from "crit" to "info".

*) Bugfix: DNS requests were not resent if initial sending of a request

failed.

*) Bugfix: the "reuseport" parameter of the "listen" directive was

ignored if the number of worker processes was specified after the
"listen" directive.

*) Bugfix: when using OpenSSL 1.1.0 or newer it was not possible to

switch off "ssl_prefer_server_ciphers" in a virtual server if it was
switched on in the default server.

*) Bugfix: SSL session reuse with upstream servers did not work with the

TLS 1.3 protocol.

</ChangeLog>