remove check for STACK_TYPE is defined

binding object doesn't work

Change-Id: I1ef08b8054108f322c79e19e2b4b556e0a375f35
diff --git a/lab-pipeline.groovy b/lab-pipeline.groovy
index 0204fd5..f9c0a63 100644
--- a/lab-pipeline.groovy
+++ b/lab-pipeline.groovy
@@ -52,11 +52,6 @@
             //
             stage ('Create infrastructure') {
 
-                // ensure STACK_TYPE is set
-                if (!binding.variables.containsKey('STACK_TYPE')) {
-                    STACK_TYPE = ''
-                }
-
                 if (STACK_TYPE == 'heat') {
                     // value defaults
                     def openstackCloud