Fix keyhash handling of initial inserts.
Fix keyhash handling of initial inserts.

Initial real_store's are called with a string of length 0,
not a NULL string.  Fix the test.

weidezhang/dht,weidezhang/dht,sit/dht,weidezhang/dht,sit/dht,sit/dht,weidezhang/dht,sit/dht,sit/dht,weidezhang/dht