tests/EventMap: Test for event past it's execution time

With the switch to std::chrono return type of GetTimeUntilEvent
we don't run into an overflow condition which happend with the previous
uint32 return value if the events scheduled execution time is in the past.
Test for this case.

(cherry picked from commit e877f988d1)

tests/common/test-EventMap.cpp

@@ -66,6 +66,13 @@ TEST_CASE("Schedule an event", "[EventMap]")
         REQUIRE(eventMap.Empty());
         REQUIRE(eventMap.GetTimeUntilEvent(EVENT_1) == Milliseconds::max());
     }
+
+    SECTION("Event is past it's execution time")
+    {
+        eventMap.Update(2000);
+
+        REQUIRE(eventMap.GetTimeUntilEvent(EVENT_1) == -1s);
+    }
 }
 
 // TODO: The semantics of this case are not well defined.