Add resolver method for session manager.

Author: ejsmith

Source/Shared/Dependency/DependencyResolverExtensions.cs

@@ -89,5 +89,9 @@ public static IEnvironmentInfoCollector GetEnvironmentInfoCollector(this IDepend
         public static ILastReferenceIdManager GetLastReferenceIdManager(this IDependencyResolver resolver) {
             return resolver.Resolve<ILastReferenceIdManager>() ?? resolver.Resolve<DefaultLastReferenceIdManager>();
         }
+
+        public static ISessionManager GetSessionManager(this IDependencyResolver resolver) {
+            return resolver.Resolve<ISessionManager>() ?? resolver.Resolve<DefaultSessionManager>();
+        }
     }
 }

Source/Shared/Plugins/Default/100_SessionManagerPlugin.cs

@@ -10,7 +10,7 @@ public void Run(EventPluginContext context) {
             if (!String.IsNullOrEmpty(context.Event.SessionId))
                 return;
 
-            var sessionManager = context.Resolver.Resolve<ISessionManager>();
+            var sessionManager = context.Resolver.GetSessionManager();
 
             string identity = context.Event.GetUserIdentity()?.Identity ?? context.Event.GetRequestInfo()?.ClientIpAddress;
             if (String.IsNullOrEmpty(identity))