Log Message:
Update databases/elasticsearch to 5.4.2

=== Enhancements

Core::
* Explicitly reject duplicate data paths

Packaging::
* Set number of processes in systemd unit file

=== Bug fixes

Aggregations::
* Terms aggregation should remap global ordinal buckets when a
* sub-aggregator is used to sort the terms

Analysis::
* PatternAnalyzer should lowercase wildcard queries when `lowercase`
* is true.

Circuit Breakers::
* Checks the circuit breaker before allocating bytes for a new big
* array

Geo::
* Fix GeoPoint FieldStats ternary logic bug
* Fix GeoDistance Ordinal for BWC

Index APIs::
* Rollover max docs should only count primaries

Nested Docs::
* Fix the `max` score mode.

Network::
* Ensure pending transport handlers are invoked for all channel
* failures

Packaging::
* When stopping via systemd only kill the JVM, not its control group

Suggesters::
* Fix context suggester to read values from keyword type field