DATAREDIS-251 - Fix tests to work against Redis 2.8.x.

Since Redis 2.8.x keyOps#getExpire() returns -2 for empty collections (RedisList/RedisSet/RedisMap). 
We're now adding a dummy entry to keep the test version agnostic. Previously getExpire() returned -1.
We also have to set the RedisAtomic(Integer|Long) to a value other than 0 to get  the value stored appropriately.

For reference see the discussion in http://redis.io/commands/ttl