get rid of varnishhtcpd upstart job

On beta deployment-cache-text1 I end up with two version of the Varnish
HTCPD purger:
- vhtcpd : from Debian package, started with init script
- varnishhtcpd : from puppet, started with upstart

The two copy race for UDP port 4827 and cause much havoc on the beta
caches.  There might be the same issue in production as well.

The Perl HTCP purger daemon has been removed in d64e7aa
 https://gerrit.wikimedia.org/r/#/c/68687/

Change-Id: If86d785362c635cfa97adb07efea222b84eacb1e
Merge "get rid of varnishhtcpd upstart job" into production