Added Update method to report on dbus

- Update method, updates timestamp and readings

Tested:
  - Added new unit tests covering update method
  - All existing unit tests are passing

Change-Id: I6b3829126d9060dbaf436cbf8e6917294dc03134
Signed-off-by: Krzysztof Grobelny <krzysztof.grobelny@intel.com>
diff --git a/src/report.cpp b/src/report.cpp
index b2ac261..6698ec3 100644
--- a/src/report.cpp
+++ b/src/report.cpp
@@ -98,6 +98,12 @@
                 "LogToMetricReportsCollection", logToMetricReportsCollection,
                 sdbusplus::vtable::property_::const_,
                 [this](const auto&) { return logToMetricReportsCollection; });
+            dbusIface.register_method("Update", [this] {
+                if (reportingType == "OnRequest")
+                {
+                    updateReadings();
+                }
+            });
         });
 
     if (reportingType == "Periodic")