util: Introduce Scheduler::cancelAllEvents to cancel all previously scheduled events

Change-Id: I11e736bec855fe4122915486faec369237cf64a6
Refs: #1757
diff --git a/src/util/scheduler.hpp b/src/util/scheduler.hpp
index bf6ada5..4287556 100644
--- a/src/util/scheduler.hpp
+++ b/src/util/scheduler.hpp
@@ -58,6 +58,12 @@
   void
   cancelEvent(const EventId& eventId);
 
+  /**
+   * \brief Cancel all scheduled events
+   */
+  void
+  cancelAllEvents();
+
 private:
   void
   onEvent(const boost::system::error_code& code);