Upgrade Elastic stack to 6.5.1

[jefflill]

We're on the 6.1.1 release right now which is several releases behind the current one. Let's update this to 6.5.1.

We're also seeing some deprecation messages due to our upgrade to OpenJDK 10 a while back. We'll try to address these too:

[2018-12-05T13:39:32.000+00:00] [INFO] [index:1] Starting [Elasticsearch]
[2018-12-05T13:39:32.000+00:00] [INFO] [index:2] ELASTICSEARCH_CLUSTER: wrt.wrt-jeff.neon-log-esdata
[2018-12-05T13:39:32.000+00:00] [INFO] [index:3] ELASTICSEARCH_NODE_MASTER: true
[2018-12-05T13:39:32.000+00:00] [INFO] [index:4] ELASTICSEARCH_NODE_DATA: true
[2018-12-05T13:39:32.000+00:00] [INFO] [index:5] ELASTICSEARCH_TCP_PORT: 5006
[2018-12-05T13:39:32.000+00:00] [INFO] [index:6] ELASTICSEARCH_HTTP_PORT: 5005
[2018-12-05T13:39:32.000+00:00] [INFO] [index:7] ELASTICSEARCH_NODE_COUNT: 3
[2018-12-05T13:39:32.000+00:00] [INFO] [index:8] ELASTICSEARCH_QUORUM: 2
[2018-12-05T13:39:32.000+00:00] [INFO] [index:9] ELASTICSEARCH_BOOTSTRAP_NODES: 10.100.24.0:5006,10.100.24.1:5006,10.100.24.2:5006
[2018-12-05T13:39:32.000+00:00] [INFO] [index:10] ES_JAVA_OPTS: -XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap
OpenJDK 64-Bit Server VM warning: Option UseConcMarkSweepGC was deprecated in version 9.0 and will likely be removed in a future release.
OpenJDK 64-Bit Server VM warning: Option UseCGroupMemoryLimitForHeap was deprecated in version 10.0 and will likely be removed in a future release.
OpenJDK 64-Bit Server VM warning: UseAVX=2 is not supported on this CPU, setting it to UseAVX=1
/docker-entrypoint.sh: line 97:    57 Killed                  gosu elasticsearch /usr/share/elasticsearch/bin/elasticsearch

[jefflill]

It looks like the UseAVX=2 warning is due to an Elasticsearch workaround for an OpenJDK compiler bug. This looks harmless:

elastic/elasticsearch#32138