Revert "adding failing concurrency test"

This reverts commit ef6033a5ec3285ed7925d138b9942214c3553e0f.
Revert "switching from memcache.SetMulti() to memcache.AddMulti() since the only reason goon.GetMulti() should add entries to memcache is if they don't exist in the memcache"

This reverts commit 0302478573e5d7aff0b9fe6060dd0f0294be98c7.