[CI] ReservedRealmIntegTests testChangingPassword failing

Build Scans:

• elasticsearch-periodic #12777 / openjdk26_checkpart4_java-matrix

Reproduction Line:

./gradlew ":x-pack:plugin:security:internalClusterTest" --tests "org.elasticsearch.xpack.security.authc.esnative.ReservedRealmIntegTests.testChangingPassword" -Dtests.seed=B925826370C6B9C9 -Dtests.locale=en-KE -Dtests.timezone=Arctic/Longyearbyen -Druntime.java=26

Applicable branches: 8.19

Reproduces locally?: N/A

Failure History: See dashboard

Failure Message:

java.lang.AssertionError: 
Expected: an empty collection
     but: <[LEAK: ByteBuf.release() was not called before it's garbage-collected. See https://netty.io/wiki/reference-counted-objects.html for more information.
Recent access records: 
#1:
	org.elasticsearch.transport.netty4.WrappedByteBuf.release(WrappedByteBuf.java:1028)
	org.elasticsearch.transport.netty4.TrashingByteBuf.release(TrashingByteBuf.java:37)
	org.elasticsearch.transport.netty4.Netty4Utils$ByteBufRefCounted.decRef(Netty4Utils.java:172)
	org.elasticsearch.common.bytes.ReleasableBytesReference.close(ReleasableBytesReference.java:103)
	org.elasticsearch.transport.InboundPipeline.releasePendingBytes(InboundPipeline.java:145)
	org.elasticsearch.transport.InboundPipeline.doHandleBytes(InboundPipeline.java:97)
	org.elasticsearch.transport.InboundPipeline.handleBytes(InboundPipeline.java:69)
	org.elasticsearch.transport.netty4.Netty4MessageInboundHandler.channelRead(Netty4MessageInboundHandler.java:54)
	io.netty.channel.Abs
[truncated]

Issue Reasons:

• [8.19] 1 consecutive failures in test testChangingPassword
• [8.19] 1 consecutive failures in step openjdk26_checkpart4_java-matrix
• [8.19] 1 consecutive failures in pipeline elasticsearch-periodic

Note: This issue was created using new test triage automation. Please report issues or feedback to es-core-infra.