Add missing mutex for retired tracers iterator

Change-Id: I795d353f66628a89fc3054f9622640deef1e18c7
Signed-off-by: davidoli <david.olien@intel.com>

level_zero/tools/source/tracing/tracing_imp.cpp

@@ -149,6 +149,7 @@ bool APITracerContextImp::isTracingEnabled() { return tracingIsEnabled; }
 // Return 1 if a reference is found.  Otherwise return 0.
 //
 ze_bool_t APITracerContextImp::testForTracerArrayReferences(tracer_array_t *tracerArray) {
+    std::lock_guard<std::mutex> lock(perThreadTracerDataMutex);
     std::list<per_thread_tracer_data_t *>::iterator itr;
     for (itr = perThreadTracerDataList.begin();
          itr != perThreadTracerDataList.end();