Disable Elasticsearch request compression by default

[joschi]

As of version 2.4.3-1, the Graylog Docker image is using Elasticsearch request compression which works with Elasticsearch but doesn't work with AWS Elasticsearch Service and might not work with all HTTP proxies used in front of Elasticsearch clusters.

graylog-docker/config/graylog.conf

Lines 228 to 231 in ee0d462

	# Enable payload compression for Elasticsearch requests.
	#
	# Default: false
	elasticsearch_compression_enabled = true

Therefore, the default should be disabled.