fix 5559: check json in extravar

public_html/deployment/plugins/rollout/awx/rollout_awx.php

@@ -177,7 +177,7 @@ class rollout_awx extends rollout_base {
         // ----- Checks:
         $sCmdChecks='';
         if($aConfig['extravars']){
-            $aTmp=json_decode($aConfig['extravars']);
+            $aTmp=json_decode($aConfig['extravars'], 1);
             if (!$aTmp || !is_array($aTmp) || !count($aTmp) ){
                 $sCmdChecks.='echo "ERROR: Value in extravars has wrong Syntax - this is no JSON: '.$aConfig['extravars'].'"; exit 1; ';                
             }