dpodctl - multiple service files and build args
dpodctl - multiple service files and build args

This allows to embed several service descriptors into the image. This is to support fat images that can be used to runs pods in different configurations.

Another change is support for build args in Dockerfile. They are supported even with pre 1.9 versions of Docker through patching the Dockerfile.

(cherry picked from commit d2be0478ba6c5b55a65ea7636bd812f8306e5768)

ibukanov/dpodctl,ibukanov/dpodctl,ibukanov/conctl,ibukanov/conctl