Raise ovftool not found exception only if artifacttype is ova

Change-Id: Ibd9ddb4ca0038085a5d48a284276bea9464c398e
Reviewed-on: http://photon-jenkins.eng.vmware.com:8082/6367
Reviewed-by: Bo Gan <ganb@vmware.com>
Tested-by: Anish Swaminathan <anishs@vmware.com>

support/image-builder/imagebuilder.py

@@ -266,7 +266,7 @@ def createImage(options):
     if not validImage:
         raise Exception("Image type/config not supported")
 
-    if 'ova' in config['image_type'] and shutil.which("ovftool") is None:
+    if 'ova' in config['artifacttype'] and shutil.which("ovftool") is None:
         raise Exception("ovftool is not available")
     workingDir = os.path.abspath(options.stage_path + "/" + config['image_type'])
     if os.path.exists(workingDir) and os.path.isdir(workingDir):