Fix multiple loading of build logs in new superuser panel

Also adds an error message if the logs fail to load

static/js/directives/ui/build-logs-view.js

@@ -164,6 +164,10 @@ angular.module('quay').directive('buildLogsView', function () {
           getBuildStatusAndLogs(build, callback);
         };
 
+        // Make sure to cancel any existing watchers first.
+        stopWatching();
+
+        // Register a new poll channel to start watching.
         $scope.pollChannel = AngularPollChannel.create($scope, conductStatusAndLogRequest, 5 * 1000 /* 5s */);
         $scope.pollChannel.start();
       };