Added environment variables to passenger-install-apache2-module in ubuntu post.pp

The install script expects the home variable to be set. Choosing /tmp
since we use it from puppet.

Error:
/usr/local/rvm/gems/ruby-1.9.3-p429/gems/passenger-4.0.5/lib/phusion_passenger/platform_info/ruby.rb:202:in `expand_path': non-absolute home (ArgumentError)