making scenarios start automatically when selected

(cherry picked from commit 3f95398)

Author: LPLafontaineB

Assets/Scripts/Gameplay/UI/NetworkSimulationUIMediator.cs

@@ -126,6 +126,7 @@ void OnScenarioChanged(int optionIndex)
         {
             var scenarioName = m_ScenariosDropdown.options[optionIndex].text;
             m_NetworkSimulator.Scenario = m_Scenarios.ContainsKey(scenarioName) ? m_Scenarios[scenarioName] : null;
+            m_NetworkSimulator.Scenario?.Start(m_NetworkSimulator);
             UpdateScenarioButton();
         }