Fixed kompose build failure

While `local` build, kompose was not recognizing `dockerfile` key
Hence it was breaking the build as mentioned in issue #832.
This PR will fix the issue.

script/test/fixtures/buildconfig/docker-compose-dockerfile.yml

@@ -0,0 +1,8 @@
+version: "2"
+
+services:
+    foo:
+        build:
+          context: .
+          dockerfile: build/Dockerfile
+        image: docker.io/cdrage/foobar