fix AgentVoqSwitchTest.rxPacketToCpu on J3

Summary: AgentVoqSwitchTest.rxPacketToCpu* is failing on J3 because     utility::addNetworkAIQosMaps() will clear the rx reason traps config added by addCpuTrafficPolicy(). This diff resolves this issue by assigned default cfg.cpuTrafficPolicy only when cpuTrafficPolicy is empty in cfg.

Reviewed By: zechengh09

Differential Revision:
D61627921

Privacy Context Container: L1125642

fbshipit-source-id: a2a81ed65e0df4a2cdb09dd02ef5c1910615885d

fboss/agent/test/utils/OlympicTestUtils.cpp

@@ -753,6 +753,9 @@ void addQosMapsHelper(
   dataPlaneTrafficPolicy.defaultQosPolicy() = qosPolicyName;
   cfg.dataPlaneTrafficPolicy() = dataPlaneTrafficPolicy;
   cfg::CPUTrafficPolicyConfig cpuConfig;
+  if (cfg.cpuTrafficPolicy()) {
+    cpuConfig = *cfg.cpuTrafficPolicy();
+  }
   cfg::TrafficPolicyConfig cpuTrafficPolicy;
   cpuTrafficPolicy.defaultQosPolicy() = cpuQosPolicyName;
   cpuConfig.trafficPolicy() = cpuTrafficPolicy;