Increase script compilations rate for Filebeat system tests

[ycombinator]

Partial backport of ##9777.

This PR ncreases the dynamic script compilations for Filebeat system tests to 1000/1m.

[ycombinator]

This PR became necessary because a recent PR to 6.x — #10385 — started failing Jenkins CI with errors like so:

not error expected but got: {u'first_char': u'[', u'log': {u'file': {u'path': u'/go/src/github.com/elastic/beats/filebeat/module/elasticsearch/audit/test/test-access.log'}}, u'service': {u'name': u'elasticsearch'}, u'beat': {u'hostname': u'943053ccf5d3', u'name': u'943053ccf5d3', u'version': u'6.7.0'}, u'error': {u'message': u'[script] Too many dynamic script compilations within, max: [75/5m]; please use indexed, or scripts with parameters instead; this limit can be changed by the [script.max_compilations_rate] setting'}, u'fileset': {u'name': u'audit', u'module': u'elasticsearch'}, u'event': {u'dataset': u'elasticsearch.audit', u'created': u'2019-01-29T02:54:42.915Z'}, u'source': u'/go/src/github.com/elastic/beats/filebeat/module/elasticsearch/audit/test/test-access.log', u'host': {u'name': u'943053ccf5d3'}, u'offset': 0, u'input': {u'type': u'log'}, u'message': u'[2018-06-19T05:16:15,549] [rest] [authentication_failed]        origin_address=[147.107.128.77], principal=[i030648], uri=[/_xpack/security/_authenticate]', u'prospector': {u'type': u'log'}}

https://beats-ci.elastic.co/job/elastic+beats+pull-request+multijob-linux/4286/beat=filebeat,label=ubuntu/testReport/junit/test_modules/Test/test_fileset_file_42_elasticsearch/

[kaiyan-sheng]

LGTM. Maybe this should be reverted after #9821 is done.