Skip the execution of the Branch and Collect algorithm if the previously scheduled execution is still running

[jachinte]

No description provided.

[jachinte]

This exception may be related to this issue:

java.util.ConcurrentModificationException
        at java.util.TreeMap$KeySpliterator.forEachRemaining(TreeMap.java:2757)
        at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
        at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
        at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
        at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
        at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
        at com.rigiresearch.middleware.graph.Graph.dependents(Graph.java:77)
        at com.rigiresearch.middleware.historian.runtime.ForkAndCollectAlgorithm.branches(ForkAndCollectAlgorithm.java:166)
        at com.rigiresearch.middleware.historian.runtime.ForkAndCollectAlgorithm.data(ForkAndCollectAlgorithm.java:140)
        at com.rigiresearch.middleware.historian.runtime.ForkAndCollectAlgorithm.data(ForkAndCollectAlgorithm.java:145)
        at com.rigiresearch.middleware.historian.runtime.ForkAndCollectAlgorithm.data(ForkAndCollectAlgorithm.java:101)
        at com.rigiresearch.middleware.historian.runtime.HistorianMonitor.collect(HistorianMonitor.java:185)
        at com.rigiresearch.middleware.historian.runtime.HistorianMonitor.lambda$start$0(HistorianMonitor.java:141)
        at it.sauronsoftware.cron4j.RunnableTask.execute(Unknown Source)
        at it.sauronsoftware.cron4j.TaskExecutor$Runner.run(Unknown Source)
        at java.lang.Thread.run(Thread.java:745)