fix reference counting for segments

[nishantmonu51]

This PR has two changes -

1. fixes ReferenceCountingQueryRunner - It now reports missing segment when query is already closed
2. fixes Queries can still access IncrementalIndex even after its closed.  #2299 by adding a swapLock to Firehydrant to make sure incrementalIndex is not swapped and closed between getSegment and increment is call.

Also removed unnecessary checks and ReportMissingSegment for null adapters.

[nishantmonu51]

AnnouncerTest failed by -
org.apache.zookeeper.KeeperException$NoNodeException: KeeperErrorCode = NoNode
https://travis-ci.org/druid-io/druid/jobs/103585051

[gianm]

👍

what do you think about also deleting RealtimePlumber.java 330:335 (block starting here: https://github.com/druid-io/druid/pull/2301/files#diff-e7c5ce8efa97c42949b01290c2bb4a47L330)?

ReportTimlineMissing for hydrants is bad; I think that code won't get called anyway (hydrants in sinks shouldn't be null, and segments in a hydrant shouldn't be null) so should be okay to delete.

[drcrallen]

This is a bug against master

[nishantmonu51]

@gianm: deleted the dead code block.

[gianm]

👍

[fjy]

@nishantmonu51 can we file an issue for the announcer test failing?

[fjy]

👍

[xvrl]

@nishantmonu51 any way we can add tests for those?