Fix startup of hhvm

There was some duplication of configs, and one outdated config
parameter, that would prevent HHVM from starting. In detail:

* Fixed default parameters
* Fixed init/upstart scripts to create a private /tmp/hhvm dir
* Install an ini file that will set the bytecode repo path

Change-Id: I27dc9321a61442632c59c0889bf85a1afa9b2c0f
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>