Move salt formulas test to xenial jenkins node

Currently some tests are not build-able on jenkins bionic nodes

Related-bug: PROD-36062
Change-Id: I99990428ae976f2e8ee9d9d091c1a5fb7f0796c4
diff --git a/test-salt-model-node.groovy b/test-salt-model-node.groovy
index 27e0909..7753b27 100644
--- a/test-salt-model-node.groovy
+++ b/test-salt-model-node.groovy
@@ -28,9 +28,11 @@
 def distribRevision = env.DISTRIB_REVISION ?: 'nightly'
 def checkouted = false
 
+def nodeLabel = 'old16.04'
+
 throttle(['test-model']) {
   timeout(time: 1, unit: 'HOURS') {
-    node("python&&docker") {
+    node(nodeLabel) {
       try{
         stage("checkout") {
           if(defaultGitRef != "" && defaultGitUrl != "") {