sensorhandler: Fix uninitialized reads

The response struct in GetSensorThresholdsResponse was not initialized
and has arbitrary data leftover from the stack. Some values like upper
and lower non-recoverable never get initialized and end up with
garbage data being reported.

Change-Id: I766f8daeb60c1ebc987cff6a24f8d8d78d64ffdd
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/sensorhandler.cpp b/sensorhandler.cpp
index e23ea48..775f651 100644
--- a/sensorhandler.cpp
+++ b/sensorhandler.cpp
@@ -474,7 +474,7 @@
 
 get_sdr::GetSensorThresholdsResponse getSensorThresholds(uint8_t sensorNum)
 {
-    get_sdr::GetSensorThresholdsResponse resp;
+    get_sdr::GetSensorThresholdsResponse resp{};
     constexpr auto warningThreshIntf =
         "xyz.openbmc_project.Sensor.Threshold.Warning";
     constexpr auto criticalThreshIntf =