:x-pack:plugin:eql:qa:rest:integTestRunner fails on 7.x release-tests

[mayya-sharipova]

There are several consecutive failures of :x-pack:plugin:eql:qa:rest:integTestRunner on 7.x release-tests with a message:

06:43:31 > Task :x-pack:qa:full-cluster-restart:v6.8.7#upgradedClusterTest
06:43:31 Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=UTF8
06:43:38 
06:43:38 > Task :x-pack:plugin:eql:qa:rest:integTestRunner FAILED
06:43:38 
06:43:38 === Standard output of node `node{:x-pack:plugin:eql:qa:rest:integTest-0}` ===
06:43:38 
06:43:38 »    ↓ errors and warnings from /dev/shm/elastic+elasticsearch+7.x+release-tests/x-pack/plugin/eql/qa/rest/build/testclusters/integTest-0/logs/es.stdout.log ↓
06:43:38 » ERROR][o.e.b.ElasticsearchUncaughtExceptionHandler] [integTest-0] uncaught exception in thread [main]
06:43:38 »  org.elasticsearch.bootstrap.StartupException: java.lang.IllegalArgumentException: unknown setting [xpack.eql.enabled] did you mean any of [xpack.sql.enabled, xpack.ml.enabled, xpack.slm.enabled, xpack.ccr.enabled, xpack.ilm.enabled, xpack.rollup.enabled, xpack.enrich.enabled, xpack.graph.enabled, xpack.vectors.enabled]?
06:43:38 »  	at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:174) ~[elasticsearch-7.7.0.jar:7.7.0]

Seems that xpack.eql.enabled setting is not available.

Log: https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+7.x+release-tests/851/console
Build scan: https://gradle-enterprise.elastic.co/s/7qpn7b33dhkzo

Log: https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+7.x+release-tests/849/console
Build scan: https://gradle-enterprise.elastic.co/s/l6eckwvwaeplm

[elasticmachine]

Pinging @elastic/es-search (:Search/EQL)

[mayya-sharipova]

Closing as a duplicate of #51541