Follow upstream's renaming of method to get current user

In gerrit's

  85f0487714e005b478eee5b28efab22bf5b7a5e2

commit, the getCurrentUser accessor got renamed to getUser. We
follow this move to allow compilation against gerrit master.

Bug: Issue 3617
Change-Id: Icc9dcbf96e8cd4002ab359a0c509fd99262c89c1
diff --git a/src/main/java/com/googlesource/gerrit/plugins/serverconfig/ServerConfigServlet.java b/src/main/java/com/googlesource/gerrit/plugins/serverconfig/ServerConfigServlet.java
index 07a67ac..18613a9 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/serverconfig/ServerConfigServlet.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/serverconfig/ServerConfigServlet.java
@@ -162,7 +162,7 @@
 
   private void audit(String what, String path, String diff) {
     String sessionId = webSession.get().getSessionId();
-    CurrentUser who = webSession.get().getCurrentUser();
+    CurrentUser who = webSession.get().getUser();
     long when = TimeUtil.nowMs();
     Multimap<String, Object> params = LinkedHashMultimap.create();
     params.put("plugin", pluginName);