Update HHVM Puppetization for Apache 2.4 + mod_proxy_fcgi

* Use mod_proxy_fcgi rather than libapache2-mod-fastcgi
* Update puppet/modules/apache/manifests/mod.pp to operations/puppet@6862b8d.
* Use scope[key] rather than scope.lookupvar(key) since we're Puppet 3+ now.
* Use hhvm-nightly package.
* Remove obsoleted mime-types hack.

Change-Id: I5c5bfecf193951645f8a97ed0e4c83f5fe366406
Lint fix

Change-Id: I64d97b18781545e36b01a3ae7586f6de15e40f12