Log Message:
Update databases/elasticsearch to 6.0.1

=== Breaking changes

Scroll::
- Fail queries with scroll that explicitely set request_cache

=== Enhancements

Core::
- Fix classes that can exit

Discovery::
- Stop responding to ping requests before master abdication

Plugin Repository S3::
- Remove S3 output stream
- Update to AWS SDK 1.11.223

Search::
- fix unnecessary logger creation

Sequence IDs::
- Log primary-replica resync failures

Snapshot/Restore::
- Remove XContentType auto detection in BlobStoreRepository

=== Bug fixes

Cluster::
- Properly format IndexGraveyard deletion date as date

Core::
- Do not set data paths on no local storage required
- Ensure threadcontext is preserved when refresh listeners are invoked
- Avoid NPE when getting build information
- When building Settings do not set SecureSettings if empty

Engine::
- Reset LiveVersionMap on sync commit
- Carry over version map size to prevent excessive resizing

Inner Hits::
- Return an empty _source for nested inner hit when filtering on a
  field that doesn't exist

Mapping::
- Fix dynamic mapping update generation.
- Fixed rounding of bounds in scaled float comparison

Nested Docs::
- Ensure nested documents have consistent version and seq_ids

Network::
- Throw UOE from compressible bytes stream reset
- Bubble exceptions when closing compressible streams

Plugin Lang Painless::
- Painless: Fix errors allowing void to be assigned to def.

Plugin Repository GCS::
- Create new handlers for every new request in
  GoogleCloudStorageService

Recovery::
- Flush old indices on primary promotion and relocation

Reindex API::
- Reindex: Fix headers in reindex action

Search::
- Fix profiling naming issues

Sequence IDs::
- Fix resync request serialization

Snapshot/Restore::
- Do not swallow exception in ChecksumBlobStoreFormat.writeAtomic()
- Delete shard store files before restoring a snapshot
- Fix snapshot getting stuck in INIT state
- Fix default value of ignore_unavailable for snapshot REST API
- Do not create directory on readonly repository

=== Upgrades

Plugin Discovery EC2::
- Upgrade AWS SDK Jackson Databind to 2.6.7.1

Plugin Discovery GCE::
- Update Google SDK to version 1.23.0