Fix heartbeat goroutine leak

[SPCDTS]

fix #142

1. In connection.StopAllConsuming(), call connection.stopHeartbeat() to avoid heartbeat goroutine leak when all queue-finish-channels closed .
2. move connection.heartbeatStop = nil from connection.stopHeartbeat() to heartbeat() to avoid dead lock while reach heartbeat error limits.
3. revise cleaner_test to match modification.
4. rename StopAllConsuming to Close for semantic reason.

[wellle]

Hey, thank you for this PR. I started to have a look at it recently and I believe I found an issue:

1. In general I don't think it's safe to do heartbeatStop = nil on the caller side, as it's not protected by the lock then.
2. More specifically consider the case where heartbeat() runs into HeartbeatErrorLimit case: In your implementation you set heartbeatStop = nil before calling Close(), so Close would actually bail out early, not stopping consumers nor the heartbeat.

I took the same approach though and opened #162.

I'm closing this PR. Thank you for your contribution though 👍