intrusion sensor: fix default reading value

As-is the updateValue method will never update the mOldValue and trigger
a redfish message.  This can be fixed by changing the default mOldValue
to "Normal".  With this change it'll detect an intrusion event at boot
and then any changes in intrusion state thereafter.

Tested:
Before change no redfish messages were being triggered.

After change asserting intrusion even triggered redfish message
and any changes to the intrusion jumper triggered redfish messages.

Change-Id: Idafa5b2dbd5501a433607981ef042a1802fab0ad
Signed-off-by: Matt Simmering <matthew.simmering@intel.com>
diff --git a/src/ChassisIntrusionSensor.hpp b/src/ChassisIntrusionSensor.hpp
index b8ac953..e3b84cf 100644
--- a/src/ChassisIntrusionSensor.hpp
+++ b/src/ChassisIntrusionSensor.hpp
@@ -27,7 +27,7 @@
   private:
     // intrusion status. 0: not intruded, 1: intruded
     std::string mValue = "unknown";
-    std::string mOldValue = "unknown";
+    std::string mOldValue = "Normal";
     std::shared_ptr<sdbusplus::asio::dbus_interface> mIface;
     sdbusplus::asio::object_server& mObjServer;
     bool mOverridenState = false;