[Tests] testNodeVersionIsUpdated stopped but didn't close it's node
[TEST] use more verbose assertion in IndicesRequestTests
[TEST] Agg may not be a instance of StringTerms, but UnmappedTerms, so use common Terms class instead
Nested: If the `_type` field isn't indexed nested docs must be filtered out.
[DOCS] Document NOT as a simple_query_string flag

Fixes #7426
Test: Fixed pluggable transport module test to support transportclient

Also made sure, that only a change of requests is tested for and not
an initial value, which might not be set in case of a node client.
Tests: Improve test coverage.

Close #7428
Context suggester: infinite loop in GeolocationContextMapping

Close #7433
[TESTS] Temporarily disable FileBasedMappingsTests.
Test: Fixed the regex in cat.indices/10_basic.yaml

And renamed the file from .yml to .yaml
[TEST] fix issue clearing fielddata breaker introduced in 6950c38a0436ec937797f01fba8d7d95e6d6225f
[TEST] Explicitly clean up actions to be intercepted in IndicesRequestTests before asserting on collected requests

This helps making sure that no further requests are collected once we start asserting on them
[Internal] discovery.id.seed is ignored

Closes #7439, Closes #7437
Stats: add segments.index_writer_max_memory to see index writer's max RAM usage before buffered documents must be written to a new segment

Closes #7438

Closes #7440
[TESTS] Temporary disable field data cache randomization.
Docs: Added link to clarify meaning of filtering in fielddata context
Core: use Java's built-in ConcurrentHashMap

It's risky to have our own snapshot of Java 8's ConcurrentHashMap:
unless we keep the sources in sync over time (and OpenJDK's version
had already diverged), then we won't get bug/performance fixes.  Users
can choose to upgrade to Java 8 to see the improvements of CHM.

Closes #7392

Closes #7296
_all: report conflict on merge and throw exception on doc_values

- _all field was never merged when mapping was updated and no conflict reported
- _all accepted doc_values format although it is always tokenized

relates to #777
closes #7377
[ENGINE] Wait until engine is started up when acquireing searcher

Today we have a small window where a searcher can be acquired but the
engine is in the state of starting up. This causes a NPE triggering a
shard failure if we are fast enough. This commit fixes this situation
gracefully.

Closes #7455
Docs: typo?

Closes #7458