Search: Do not force the post-filter to be loaded into a BitSet.

Close #8488
Docs: Fix typo in the javadoc for #tieBreaker()

Closes #8503
fix of Bulk update child doc, NPE error message when parent is not specified #8365
  - Throw an RoutingMissingException instead of NPE
Bulk indexing issue - missing parent routing causes NullPointerException.
Now each error is reported in bulk response rather than causing entire bulk to fail.
Added a Junit test but the use of TransportClient means the error is manifested differently to a REST based request - instead of a NullPointer the whole of the bulk request failed with a RoutingMissingException. Changed TransportBulkAction to catch this exception and treat it the same as the existing logic for a ElasticsearchParseException - the individual bulk request items are flagged and reported individually rather than failing the whole bulk request.

Closes #8365
Snapshot/Restore: restore of indices that are only partially available in the cluster

Fixes the issue with restoring of an index that had only some of its primary shards allocated before it was closed.

Fixes #8224
Snapshot/Restore: keep the last legacy checksums file at the end of restore

 This commit fixes the issue caused by restore process deleting all legacy checksum files at the end of restore process. Instead it keeps the latest version of the checksum intact. The issue manifests itself in losing checksum for all legacy files restored into post 1.3.0 cluster, which in turn causes unnecessary snapshotting of files that didn't change.

Fixes #8119
Test: force merge index in the end of IndexStatsTests.throttleStats

This works around slow IO (fsync) causing the test-framework cleanup
to timeout at 30 seconds when trying to delete the index.

Closes #8528
[TEST] Register data.path for all nodes on close in InternalTestCluster

We need to register those data paths otherwise we might miss path that
need to get cleaned when using local gatway etc. which can otherwise
cause imports of dangeling indices.
[STORE] Use DistributorDirectory only if there are more than one data direcotry

We don't need the overhead of DistributorDirectory if there is only a single directory
in the distributor.
[CORE] Ban all useage of Future#cancel(true)

Interrupting a thread while blocking on an NIO Read / Write Operation
can cause a file to be closed due to the interrupts. This can have unpredictable
effects when files are open by index readers etc. we should prevent interruptions
across the board if possible.

Closes #8494