fix: do not execute already executing browsers

This was causing iframe reloads on IE8/IE9. These browsers use xhr-polling and socket.io does re-connects pretty often. We need to start execution only when the browser connects for the first time, no other re-connects.

lib/server.js

@@ -105,15 +105,15 @@ var start = function(injector, config, launcher, globalEmitter, preprocess, file
         }]).instantiate(browser.Browser);
 
         newBrowser.init();
+
+        // execute in this browser immediately
+        if (config.singleRun) {
+          newBrowser.execute(config.client);
+          singleRunBrowsers.add(newBrowser);
+        }
       }
 
       replySocketEvents();
-
-      // execute in this browser immediately
-      if (config.singleRun) {
-        newBrowser.execute(config.client);
-        singleRunBrowsers.add(newBrowser);
-      }
     });
   });