Replace uWSGI's broken init.d scripts with Upstart job def

The init.d scripts for uWSGI leave processes hanging around and starts new
processes before these lingering processes have been terminated. They're also
long and complicated and difficult to reason about. This patch replaces them
with an Upstart task, which is a pattern I've used elsewhere (EventLogging,
mwprof, Carbon) and that I find works very well.

Change-Id: I8c214e0fd18c0f12768f016272a261b0f4476aa8
Merge "Replace uWSGI's broken init.d scripts with Upstart job def" into production