Issue describing the changes in this PR

resolves 138

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes are added to the CHANGELOG.md
• I have added all required tests (Unit tests, E2E tests)

Additional information

Additional PR information

For a sample orchestration function

    @FunctionName("EternalOrchestrator")
    public void startWorkflowSchedule(@DurableOrchestrationTrigger(name = "runtimeState") TaskOrchestrationContext ctx) 
     {
        LOGGER.info("Doing something in the cleanup loop");

        ctx.createTimer(Duration.ofSeconds(60)).await();

        ctx.continueAsNew(null);
     }

The invocation process complete twice:

1. First time at

   durabletask-java/client/src/main/java/com/microsoft/durabletask/OrchestrationRunner.java

   Line 66 in 4a204cd

   ctx.complete(output);

   ctx.complete(null)
2. Second time at

   durabletask-java/client/src/main/java/com/microsoft/durabletask/TaskOrchestrationExecutor.java

   Line 60 in 4a204cd

   context.complete(null);

   
   This is the one causing exception as isCompleted flag is already set to true at the first complete.

Update the condition check at 2 to avoid repeating complete.