Currently memcache only listens to the internal_api IP. We want to
make it listen to both localhost and internal_api IP because in the
future some services on some roles may want to just use the localhost
memcached instance instead of the using multiple memcached servers
over the network as it is the case currently.
As suggested by Takashi we check the ip version in MemcachedNetwork
in order to decide if we should listen to ::1 or 127.0.0.1
(cherry picked from commit