applicationserver: provision stub HHVM role on Beta Labs

Provisions HHVM to run on port 9000 using the FastCGI server.

TODOs:

* Configure Apache to delegate to the HHVM interpreter based on
  the presence of a cookie, probably using SetEnvIf.
* Parametrize server.hdf

Change-Id: I2833af31d6a9732adce9ad1b3d0b342120c940e1