runTask: Check out branch with different refspec

vars/runTask.groovy

@@ -18,7 +18,7 @@ def call(String task, String branch, String repo, String phpversion, String data
                             $class: 'GitSCM',
                             branches: [
                                 [
-                                    name: "*/${branch}"
+                                    name: "${branch}"
                                 ]
                             ],
                             doGenerateSubmoduleConfigurations: false,