CI: GatewayIndexStateIT#testIndexDeletionWhenNodeRejoins fails

[dnhatn]

This test fails because it does not release all acquired searchers during the primary-replica resync.

com.carrotsearch.randomizedtesting.ResourceDisposalError: Resource in scope SUITE failed to close. Resource was registered from thread Thread[id=47, name=elasticsearch[node_t0][refresh][T#1], state=RUNNABLE, group=TGRP-GatewayIndexStateIT], registration stack trace below.

Caused by: java.lang.AssertionError: Unreleased searchers found
org.elasticsearch.index.engine.InternalEngine.newChangesSnapshot(InternalEngine.java:2403)
		at org.elasticsearch.index.engine.InternalEngine.readHistoryOperations(InternalEngine.java:482)
		at org.elasticsearch.index.shard.IndexShard.getHistoryOperations(IndexShard.java:1650)
		at org.elasticsearch.index.shard.PrimaryReplicaSyncer.resync(PrimaryReplicaSyncer.java:92)

CI instances:

• https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+intake/2707/console
• https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+intake/2725/console

[elasticmachine]

Pinging @elastic/es-distributed

[dnhatn]

Another instance: https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+periodic/7023/console