Two big differences of haproxy are that haproxy does not use separate files
for certificates and that the time in logs are in milliseconds, whereas with
httpd it was microseconds. For certificates, when using caucase to generate
haproxy's own server certificate we specify the same file as cert and key as
caucase supports this and instead of maintaining directories of CA and CRL
for client certificates (used by shared frontend), we build PEM files
containing all CA certificates and all CRL together.
For the logs, we use a new version of apachedex which supports `%{ms}T` for
durations.

Tests have been modified a bit, because haproxy uses HTTP/2.0 and not 1.1
like httpd was doing several haproxy features (keep alive and gzip
compression) are only available when backend uses HTTP/1.1, so we adjusted
tests to use a 1.1 backend.

There was also differences with logs, because of the time being in milliseconds.

TestPublishedURLIsReachableMixin._checkERP5IsReachable was also updated, it
was working by chance because when accessed behind httpd->haproxy->zope, zope
was producing a redirect URL that was the URL of haproxy, which could be
resolved by chance. This test was updated to access zope with a path that
contains VirtualHostMonster magic, as the shared frontend ( with "zope" software
type) is supposed to set.

This should hopefuly solve the "502 Proxy Error" that we are observing with httpd.