presence: Add sensor to redundancy policy api

Include a reference to the sensor changing state when sensor
implementations ping the policy object.

This allows policy logic based on multiple sensors, simultaneously.

Change-Id: I44cf00c7ecd220d0cc99e51ca6093bac6da7343c
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/presence/fallback.hpp b/presence/fallback.hpp
index a1a5b29..280ef1c 100644
--- a/presence/fallback.hpp
+++ b/presence/fallback.hpp
@@ -55,8 +55,9 @@
          *
          * @param[in] present - The new presence state according
          *             to the active sensor.
+         * @param[in] sensor - The sensor that changed state.
          */
-        void stateChanged(bool present) override;
+        void stateChanged(bool present, PresenceSensor& sensor) override;
 
         /**
          * @brief monitor