Name resolution of cache_peer fails in Squid when the hostname is upper case

Issue

• The squid proxy does not connect to other proxies in the hierarchy.

• A message similar to the following may appear in /var/log/squid/cache.log:

  2018/10/04 08:10:52 kid1| Configuring Parent PROXY-HOSTNAME/3128/3130
  2018/10/04 08:10:52 kid1| WARNING: DNS lookup for 'PROXY-HOSTNAME' failed!