plugins/task: Fix cache name in Preloader

Change cache name from optionalTaskByName to optionalTaskByExpression,
since the cache key is expression instead of the name of task.

Change-Id: I6757b4d3ea00c495527f921f9bc4c45a76ba578e

src/main/java/com/googlesource/gerrit/plugins/task/Preloader.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/task/Preloader.java b/src/main/java/com/googlesource/gerrit/plugins/task/Preloader.java
index 6af576c..6d6900d 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/task/Preloader.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/task/Preloader.java
@@ -26,17 +26,17 @@
 /** Use to pre-load a task definition with values from its preload-task definition. */
 public class Preloader {
   protected final TaskConfig config;
-  protected final Map<String, Optional<Task>> optionalTaskByName = new HashMap<>();
+  protected final Map<String, Optional<Task>> optionalTaskByExpression = new HashMap<>();
 
   public Preloader(TaskConfig config) {
     this.config = config;
   }
 
   public Optional<Task> preloadOptional(TaskExpression expression) throws ConfigInvalidException {
-    Optional<Task> task = optionalTaskByName.get(expression.getKey());
+    Optional<Task> task = optionalTaskByExpression.get(expression.getKey());
     if (task == null) {
       task = loadOptional(expression);
-      optionalTaskByName.put(expression.getKey(), task);
+      optionalTaskByExpression.put(expression.getKey(), task);
     }
     return task;
   }