stream segment can't be submit After the coordinator leader is changed

Env:

2 coordinator node: node-0,node-1

When the leader was changed to the node-0, the stream segment building job can't be submitted.

The remote persisted segment can't be deleted. 

Find the error log in the coordinator leader node:

```

2021-06-10 00:01:41,601 INFO [streaming_job_submitter-thread-1] coordinate.BuildJobSubmitter:203 : The cube: xxxxxxxxx  segment:20210603080000_20210603090000 is ready to be promoted.
2021-06-10 00:01:41,601 ERROR [streaming_job_submitter-thread-1] coordinate.BuildJobSubmitter:136 : Unexpected error
java.lang.NullPointerException
at org.apache.kylin.stream.coordinator.coordinate.ReceiverClusterManager.checkPreviousSegmentReady(ReceiverClusterManager.java:626)
at org.apache.kylin.stream.coordinator.coordinate.ReceiverClusterManager.segmentBuildComplete(ReceiverClusterManager.java:520)
at org.apache.kylin.stream.coordinator.coordinate.BuildJobSubmitter.traceEarliestSegmentBuildJob(BuildJobSubmitter.java:205)
at org.apache.kylin.stream.coordinator.coordinate.BuildJobSubmitter.doRun(BuildJobSubmitter.java:145)
at org.apache.kylin.stream.coordinator.coordinate.BuildJobSubmitter.run(BuildJobSubmitter.java:133)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)

```

In the frontend, there is no the segment