Warn instead of failing hard on bad poolConfig parameters

* Warn instead of failing hard on bad poolConfig parameters
* Apparently Redis 2.8 changed the return value of TTL for non-existent keys to -2 (instead of -1), so I've updated the tests with the assumption they would be run against 2.8. The core code still works, and actually slightly better. There's two cases where it checks the TTL, and if it's -1, it will issue the EXPIRE command. For a non-existent key, that would previously call expire, but now it will actually skip the EXPIRE on the key that does not exist, saving one round trip.
* The taglib tests failed for me locally because there's an assumption that they run in the order of the file, though grails does not guarantee that behavior