The loading and creation of the Memcache ring in the middleware is
rather interesting. It not only reads the config file, but also may
look for a `/etc/swift/memcache.conf`. Further, we are know are
looking at using the MemcacheRing client in more places.
So this patch moves the config reading from the middleware and
into a `load_memcache` helper method in swift/common/memcached.py.
Drive-by: cleanup unused stuff in middleware test module
Change-Id: I028722facfbe3ff8092b6bdcc931887a169cc49a
a8516e1510