Update QueryIteratorWrapper to performClose and performRequestCancel

[Aklakan]

Pull request Description: Fix a rare race condition that can cause a test failure during build. QueryIteratorWrapper is updated to reuse QueryIteratorBase.performClose and performRequestCancel. These methods ensure that the reference to the delegate iterator remains unchanged during the "if not null" check and the subsequent cancel / close action.

Should be unrelated to #3063.

Below is the build error I got for the first time since contributing the TestQueryExecutionCancel test case.

[ERROR] Tests run: 21, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 1.723 s <<< FAILURE! -- in org.apache.jena.sparql.api.TestQueryExecutionCancel
[ERROR] org.apache.jena.sparql.api.TestQueryExecutionCancel.test_cancel_concurrent_1 -- Time elapsed: 0.091 s <<< ERROR!
java.lang.NullPointerException
	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
	at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
	at java.base/java.util.concurrent.ForkJoinTask.getThrowableException(ForkJoinTask.java:564)
	at java.base/java.util.concurrent.ForkJoinTask.reportException(ForkJoinTask.java:591)
	at java.base/java.util.concurrent.ForkJoinTask.invoke(ForkJoinTask.java:689)
	at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateParallel(ForEachOps.java:159)
	at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateParallel(ForEachOps.java:173)
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:233)
	at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596)
	at java.base/java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:765)
	at org.apache.jena.sparql.api.TestQueryExecutionCancel.runConcurrentAbort(TestQueryExecutionCancel.java:385)
	at org.apache.jena.sparql.api.TestQueryExecutionCancel.test_cancel_concurrent(TestQueryExecutionCancel.java:365)
	at org.apache.jena.sparql.api.TestQueryExecutionCancel.test_cancel_concurrent_1(TestQueryExecutionCancel.java:342)
	at java.base/java.lang.reflect.Method.invoke(Method.java:569)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.lang.Thread.run(Thread.java:840)
Caused by: java.lang.NullPointerException: Cannot invoke "org.apache.jena.sparql.engine.QueryIterator.cancel()" because "this.iterator" is null
	at org.apache.jena.sparql.engine.iterator.QueryIteratorWrapper.requestCancel(QueryIteratorWrapper.java:56)
	at org.apache.jena.sparql.engine.iterator.QueryIteratorBase.cancel(QueryIteratorBase.java:212)
	at org.apache.jena.sparql.engine.iterator.QueryIteratorWrapper.requestCancel(QueryIteratorWrapper.java:56)
	at org.apache.jena.sparql.engine.iterator.QueryIteratorBase.cancel(QueryIteratorBase.java:212)
	at org.apache.jena.sparql.exec.QueryExecDataset.abort(QueryExecDataset.java:162)
	at org.apache.jena.sparql.exec.QueryExecutionAdapter.abort(QueryExecutionAdapter.java:228)
	at org.apache.jena.sparql.exec.QueryExecutionCompat.abort(QueryExecutionCompat.java:173)
	at org.apache.jena.sparql.api.TestQueryExecutionCancel.lambda$runConcurrentAbort$9(TestQueryExecutionCancel.java:404)
	at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
	at java.base/java.util.AbstractList$RandomAccessSpliterator.forEachRemaining(AbstractList.java:720)
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
	at java.base/java.util.stream.ForEachOps$ForEachTask.compute(ForEachOps.java:290)
	at java.base/java.util.concurrent.CountedCompleter.exec(CountedCompleter.java:754)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182)
	at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165)

---

By submitting this pull request, I acknowledge that I am making a contribution to the Apache Software Foundation under the terms and conditions of the Contributor's Agreement.

---

See the Apache Jena "Contributing" guide.