Docs: note about confusing disk threshold settings
[DOCS] Corrected syntax error in search curl cmd

Closes #8447
Internal: Don't pass acceptdocs down to nonNestedDocsFilter in ParentsFilter

Closes #8461
Docs: Fix typo in the javadoc for #tieBreaker()

Closes #8503
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] 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.

Conflicts:
	src/test/java/org/elasticsearch/test/InternalTestCluster.java