Fixed issue with wrong timestamp

Telemetry service used steady_clock for generating timestamps, but it
produced incorrect time. This change makes telemetry service use
steady_clock for intervals and system_clock for timestamps.

Changed readings timestamp to display current timestamp instead of a
time when reading was received.

Tested:
- correct timestamp is visible on dbus
- other telemetry service features are still working

Change-Id: Ic49f45640532cfffaeff5e0bd5591e6d99e5def5
Signed-off-by: Krzysztof Grobelny <krzysztof.grobelny@intel.com>
diff --git a/src/on_change_threshold.hpp b/src/on_change_threshold.hpp
index 7eb1f6d..61c75d5 100644
--- a/src/on_change_threshold.hpp
+++ b/src/on_change_threshold.hpp
@@ -25,13 +25,13 @@
     {}
 
     void initialize() override;
-    void sensorUpdated(interfaces::Sensor&, uint64_t) override;
-    void sensorUpdated(interfaces::Sensor&, uint64_t, double) override;
+    void sensorUpdated(interfaces::Sensor&, Milliseconds) override;
+    void sensorUpdated(interfaces::Sensor&, Milliseconds, double) override;
 
   private:
     const Sensors sensors;
     const std::vector<std::string> sensorNames;
     const std::vector<std::unique_ptr<interfaces::TriggerAction>> actions;
 
-    void commit(const std::string&, uint64_t, double);
+    void commit(const std::string&, Milliseconds, double);
 };