JIRA: https://jira.spring.io/browse/INT-1463
An existing `QueueChannel#getRemainingCapacity()` is based on the `BlockingQueue#getRemainingCapacity()` which is always `Integer.MAX_VALUE`
and doesn't reflect reality for provided `capacity`
* Fix `PriorityChannel` to return `upperBound.availablePermits()` for `getRemainingCapacity()`
* Add test for `PriorityChannel` on the matter
* Also increase `reply-timeout` for `<int-redis:queue-outbound-gateway>` in `RedisQueueGatewayIntegrationTests-context.xml` from 1 sec to 10 secs
cfa00c5707