Save computed graph to disk if build is complete

Author: timja

src/main/java/io/jenkins/plugins/pipelinegraphview/utils/PipelineGraphViewCache.java

@@ -44,6 +44,9 @@ public PipelineGraph getGraph(WorkflowRun run, Supplier<PipelineGraph> compute)
             return compute.get();
         }
         CachedPayload payload = load(run);
+        if (payload.graph != null) {
+            return payload.graph;
+        }
         synchronized (payload) {
             if (payload.graph == null) {
                 payload.graph = compute.get();
@@ -59,6 +62,9 @@ public PipelineStepList getAllSteps(WorkflowRun run, Supplier<PipelineStepList>
             return compute.get();
         }
         CachedPayload payload = load(run);
+        if (payload.allSteps != null) {
+            return payload.allSteps;
+        }
         synchronized (payload) {
             if (payload.allSteps == null) {
                 payload.allSteps = compute.get();