Added fallback to INSTALL property in lab pipeline

Change-Id: I44e1806bde0ce3a19f6e8196407b23bf080bfafe
diff --git a/lab-pipeline.groovy b/lab-pipeline.groovy
index 83b3526..110dd12 100644
--- a/lab-pipeline.groovy
+++ b/lab-pipeline.groovy
@@ -51,6 +51,18 @@
 salt = new com.mirantis.mk.Salt()
 test = new com.mirantis.mk.Test()
 
+// try to get STACK_INSTALL or fallback to INSTALL if exists
+try {
+  def temporary = STACK_INSTALL
+} catch (MissingPropertyException e) {
+  try {
+    STACK_INSTALL = INSTALL
+  } catch (MissingPropertyException e) {
+    common.errorMsg("Property STACK_INSTALL or INSTALL not found!")
+  }
+}
+
+
 _MAX_PERMITTED_STACKS = 2
 overwriteFile = "/srv/salt/reclass/classes/cluster/overwrite.yml"