[hotfix][yarn] userJarFiles can be a local variable

This closes apache#8264.

flink-yarn/src/main/java/org/apache/flink/yarn/AbstractYarnClusterDescriptor.java

@@ -100,6 +100,7 @@
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 import static org.apache.flink.configuration.ConfigConstants.ENV_FLINK_LIB_DIR;
 import static org.apache.flink.runtime.entrypoint.component.FileJobGraphRetriever.JOB_GRAPH_FILE_PATH;
@@ -143,10 +144,6 @@ public abstract class AbstractYarnClusterDescriptor implements ClusterDescriptor
 
  private String applicationType;
 
- /** Optional Jar file to include in the system class loader of all application nodes
- * (for per-job submission). */
- private final Set<File> userJarFiles = new HashSet<>();
-
  private YarnConfigOptions.UserJarInclusion userJarInclusion;
 
  public AbstractYarnClusterDescriptor(
@@ -739,12 +736,11 @@ public ApplicationReport startAppMaster(
  1));
  }
 
- if (jobGraph != null) {
- // add the user code jars from the provided JobGraph
- for (org.apache.flink.core.fs.Path path : jobGraph.getUserJars()) {
- userJarFiles.add(new File(path.toUri()));
- }
- }
+ final Set<File> userJarFiles = (jobGraph == null)
+ // not per-job submission
+ ? Collections.emptySet()
+ // add user code jars from the provided JobGraph
+ : jobGraph.getUserJars().stream().map(f -> f.toUri()).map(File::new).collect(Collectors.toSet());
 
  // local resource map for Yarn
  final Map<String, LocalResource> localResources = new HashMap<>(2 + systemShipFiles.size() + userJarFiles.size());