Use MetaDataUpdate.Server instead of MetaDataUpdate.User in cache loader

Cache loading may be done in a different thread and we may not have the
current user defined for that thread. We also do not need the current
user when loading the serviceuser.db.

Change-Id: I5659dae7a38c6ec75053953ffe892307a8fd0fde
diff --git a/src/main/java/com/googlesource/gerrit/plugins/serviceuser/StorageCache.java b/src/main/java/com/googlesource/gerrit/plugins/serviceuser/StorageCache.java
index 81f543a..0378347 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/serviceuser/StorageCache.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/serviceuser/StorageCache.java
@@ -68,13 +68,13 @@
 
   static class Loader extends CacheLoader<Object, Config> {
     private final Provider<Bare> configProvider;
-    private final MetaDataUpdate.User metaDataUpdateFactory;
+    private final MetaDataUpdate.Server metaDataUpdateFactory;
     private final AllProjectsName allProjects;
 
     @Inject
     Loader(
         Provider<ProjectLevelConfig.Bare> configProvider,
-        MetaDataUpdate.User metaDataUpdateFactory,
+        MetaDataUpdate.Server metaDataUpdateFactory,
         AllProjectsName allProjects) {
       this.configProvider = configProvider;
       this.metaDataUpdateFactory = metaDataUpdateFactory;