Fix some aspnet tests to be labeled as IIS instead of nginx

Should fix #521.

aspnet/benchmark_config

@@ -31,7 +31,7 @@
       "language": "C#",
       "orm": "Raw",
       "platform": "NET",
-      "webserver": "nginx",
+      "webserver": "IIS",
       "os": "Windows",
       "database_os": "Linux",
       "display_name": "aspnet-jsonnet",
@@ -49,7 +49,7 @@
       "language": "C#",
       "orm": "Raw",
       "platform": "NET",
-      "webserver": "nginx",
+      "webserver": "IIS",
       "os": "Windows",
       "database_os": "Linux",
       "display_name": "aspnet-svcstk",