The documentation could be understood like the following:
memcache_servers from memcache.conf is always used if set, even if
memcache_servers in proxy-server.conf is set.
This is clearly not the case, as proxy-server.conf has a higher priority
if it memcache_servers is set there.
Change-Id: I967c7e80796a0e296c5c65bd097df1669d16203e