image_build_tag variable not defined during execution

Change-Id: I8c319bc281f2569547b54f6b97178246248af4f5
diff --git a/scripts/imagebuilder.py b/scripts/imagebuilder.py
index b48edea..1b1426d 100755
--- a/scripts/imagebuilder.py
+++ b/scripts/imagebuilder.py
@@ -1242,7 +1242,7 @@
 
         if self.dc is not None:
 
-            build_tag = "%s:%s" % (image.name, image.tags[0])
+            image_build_tag = "%s:%s" % (image.name, image.tags[0])
 
             buildargs = image.buildargs()
             context_tar = image.context_tarball()