Fix unit test memory leak

Shutdown ASP.NET AppDomains after running each SpecFlow scenario.

--HG--
branch : dev

src/Orchard.Specs/Bindings/WebAppHosting.cs

@@ -14,10 +14,10 @@ using HtmlAgilityPack;
 using log4net.Appender;
 using log4net.Core;
 using log4net.Repository;
+using NUnit.Framework;
 using Orchard.Specs.Hosting;
 using Orchard.Specs.Util;
 using TechTalk.SpecFlow;
-using NUnit.Framework;
 
 namespace Orchard.Specs.Bindings {
     [Binding]
@@ -27,6 +27,9 @@ namespace Orchard.Specs.Bindings {
         private HtmlDocument _doc;
         private MessageSink _messages;
 
+        public WebAppHosting() {
+        }
+
         public WebHost Host {
             get { return _webHost; }
         }
@@ -36,6 +39,14 @@ namespace Orchard.Specs.Bindings {
             set { _details = value; }
         }
 
+        [AfterScenario]
+        public void AfterScenario() {
+            if (_webHost != null) {
+                _webHost.Dispose();
+                _webHost = null;
+            }
+        }
+
         [Given(@"I have a clean site")]
         public void GivenIHaveACleanSite() {
             GivenIHaveACleanSiteBasedOn("Orchard.Web");