Stop SPAMming Gerrit logs with 'Logging context is not empty'

Gerrit v3.1 started SPAMming error_log with a continuous series
of warnings that the LoggingContext was not empty at the start
of the execution of LoggingContextAwareRunnable.

The warning is misleading because it doesn't reflect
the situation where the logging context is dirty but just
tells that at the start of the execution there is already one
of the following elements of the thread-local storage already
allocated:
- tags
- forceLogging
- performanceLogging
- performanceLogRecords

Of the four objects stored in the thread-local storage,
the performanceLogRecords is created well before the start
of the execution and therefore will always be not null when
the Callable wrapper gets invoked.

Remove the condition on the performanceLogRecords so that
the warning will fire if there is a real context dirty
detected, apart from the performanceLogRecords that will be
always set to a non-null value.

Bug: Issue 12443
Change-Id: I6cf7db36165f7653ddb178f0cabe61faa13696e2
diff --git a/java/com/google/gerrit/server/logging/LoggingContext.java b/java/com/google/gerrit/server/logging/LoggingContext.java
index 36c7e9e..8e786fc 100644
--- a/java/com/google/gerrit/server/logging/LoggingContext.java
+++ b/java/com/google/gerrit/server/logging/LoggingContext.java
@@ -81,10 +81,7 @@
   }
 
   public boolean isEmpty() {
-    return tags.get() == null
-        && forceLogging.get() == null
-        && performanceLogging.get() == null
-        && performanceLogRecords.get() == null;
+    return tags.get() == null && forceLogging.get() == null && performanceLogging.get() == null;
   }
 
   public void clear() {