[JENKINS-67624] FileAlreadyExistsException on startup (jenkinsci#7027)

(cherry picked from commit 6b0dc18)

Author: basil

core/src/main/java/hudson/Util.java

@@ -1778,15 +1778,32 @@ public static Path createDirectories(@NonNull Path dir, FileAttribute<?>... attr
             if (Files.isDirectory(dir)) {
                 return dir;
             } else {
-                return Files.createDirectory(dir, attrs);
+                try {
+                    return Files.createDirectory(dir, attrs);
+                } catch (FileAlreadyExistsException e) {
+                    if (Files.isDirectory(dir)) {
+                        // a concurrent caller won the race
+                        return dir;
+                    } else {
+                        throw e;
+                    }
+                }
             }
         }
 
         Path child = parent;
         for (Path name : parent.relativize(dir)) {
             child = child.resolve(name);
             if (!Files.isDirectory(child)) {
-                Files.createDirectory(child, attrs);
+                try {
+                    Files.createDirectory(child, attrs);
+                } catch (FileAlreadyExistsException e) {
+                    if (Files.isDirectory(child)) {
+                        // a concurrent caller won the race
+                    } else {
+                        throw e;
+                    }
+                }
             }
         }