Async cache store shutdown timeout default value should be -1

We should strive for correctness really.

Better to have someone complain about Infinispan not finishing rather than missing data in the cache store.

To avoid confusion, we should wait for a bit of time, i.e. 1 minute, and then if the async store has not finished yet, log a WARN message indicating what's up, but then carry on waiting forever (or whatever the defined user time - minus the 60 seconds) by default.

If the user defined timeout is less than 60 seconds, wait that long.