twemproxy/nutcracker: add restart script to be used post-migration

We are migrating to a new version of the nutcracker/twemproxy package,
with proper upstart integration and a sane package structure. That also
means that the service will be renamed from 'twemproxy' to 'nutcracker',
and this should reflect in scap before we can deploy puppet changes.

Change-Id: I63f6487bed936806555af0fee7843ffb600ff3fc
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>