Update label for salt-formula tests

Jenkins nodes labeled "old16.04" were deleted

Change-Id: If57a195688f1abeb65858cb5527bc57fbde18f40
diff --git a/test-salt-formulas-env.groovy b/test-salt-formulas-env.groovy
index 5c3b894..e2b164c 100644
--- a/test-salt-formulas-env.groovy
+++ b/test-salt-formulas-env.groovy
@@ -27,7 +27,7 @@
   env.GERRIT_BRANCH = GERRIT_PARENT_BRANCH
 }
 
-def nodeLabel = 'old16.04'
+def nodeLabel = 'docker'
 
 def checkouted = false
 def openstackTest = false