Barbican uWSGI stats server listen on localhost

The current uWSGI Upstart script starts the stats server listening
on all IPs. In order to reduce the attack surface, this patch modifies
the Upstart script so that the stats server starts listening on
localhost only.

Closes-Bug: #1288881
Change-Id: I6141e665433d418b8cbecc4f065b8a3710310d29
Merge "Barbican uWSGI stats server listen on localhost"