Log Message:
Update databases/elasticsearch to 5.4.1.

=== Enhancements

Aggregations::
- Allow scripted metric agg to access `_score`

Core::
- Improve bootstrap checks error messages

Internal::
- Log JVM arguments on startup

Network::
- Disable the Netty recycler in the client
- Remove Netty logging hack
- Set available processors for Netty

Snapshot/Restore::
- Ensure every repository has an incompatible-snapshots blob

Stats::
- Show JVM arguments

=== Bug fixes

Aggregations::
- Fix ArrayIndexOutOfBoundsException when no ranges are specified in
  the query

Allocation::
- Discard stale node responses from async shard fetching

Core::
- Fix cache expire after access

Index APIs::
- Fix legacy GeoPointField decoding in FieldStats
- Validates updated settings on closed indices

Internal::
- Remove `_UNRELEASED` from Version constants for released versions
- Avoid race when shutting down controller processes
- Fix NPE if field caps request has a field that exists not in all
  indices

More Like This::
- Pass over _routing value with more_like_this items to be retrieved

Network::
- Notify onConnectionClosed rather than onNodeDisconnect to prune
  transport handlers
- SniffNodesSampler should close connection after handling responses

Packaging::
- Handle parentheses in batch file path

Percolator::
- Fix range queries with date range based on current time in
  percolator queries.

Plugin Repository HDFS::
- Fixing permission errors for `KERBEROS` security mode for HDFS
  Repository

Plugins::
- X-Pack plugin download fails on Windows desktop [ISSUE]
- Fix plugin installation permissions

Reindex API::
- Reindex: don't duplicate _source parameter
- Add qa module that tests reindex-from-remote against pre-5.0
  versions of Elasticsearch

Scroll::
- Fix single shard scroll within a cluster with nodes in version `>=
  5.3` and `<= 5.3`

Search::
- Fix ExpandSearchPhase when response contains no hits
- Include all aliases including non-filtering in  `_search_shards`
  response

Settings::
- Allow resetting settings that use an IP validator

Snapshot/Restore::
- Removes completed snapshot from cluster state on master change
- Fix inefficient (worst case exponential) loading of snapshot
  repository

=== Upgrades

Core::
- Upgrade to Lucene 6.5.1

Network::
- Upgrade to Netty 4.1.11.Final
- Upgrade Netty to 4.1.10.Final