Change tracing to TRACE_TAG_SERVER instead of TRACE_TAG_ACTIVITY_MANAGER.

That makes it easier to time it using atrace / systrace....

Bug: 133242016
Test: manual verification

Change-Id: Ib1596a227194c06e09deee68fbb9c51926ff2b24
diff --git a/src/com/android/internal/car/CarServiceHelperService.java b/src/com/android/internal/car/CarServiceHelperService.java
index b942b46..f8842d4 100644
--- a/src/com/android/internal/car/CarServiceHelperService.java
+++ b/src/com/android/internal/car/CarServiceHelperService.java
@@ -276,7 +276,7 @@
             return;
         }
         TimingsTraceLog traceLog = new TimingsTraceLog("SystemServerTiming",
-                Trace.TRACE_TAG_ACTIVITY_MANAGER);
+                Trace.TRACE_TAG_SYSTEM_SERVER);
         traceLog.traceBegin("User0Unlock");
         try {
             // This is for force changing state into RUNNING_LOCKED. Otherwise unlock does not