Upgrade from 1.15.0 to 1.15.1.
<ChangeLog>
*) Feature: the "random" directive inside the "upstream" block.
*) Feature: improved performance when using the "hash" and "ip_hash"
directives with the "zone" directive.
*) Feature: the "reuseport" parameter of the "listen" directive now uses
SO_REUSEPORT_LB on FreeBSD 12.
*) Bugfix: HTTP/2 server push did not work if SSL was terminated by a
proxy server in front of nginx.
*) Bugfix: the "tcp_nopush" directive was always used on backend
connections.
*) Bugfix: sending a disk-buffered request body to a gRPC backend might
fail.
</ChangeLog>