INT-3177: generic RedisTemplate for PublishingMH

JIRA: https://jira.springsource.org/browse/INT-3177

* Change `RedisPublishingMessageHandler.StringRedisTemplate` to `RedisTemplate<?, ?>`
* Don't provide `serializer` to the `template`
* Use `serializer` directly for values which are not `byte[]`
* Add `RedisAvailableTests#awaitContainerSubscribed` for tests to avoid race conditions
* Refactor some tests
* Add test for `byte[]` payload