js: Add test that containers are de-duped
js: Add test that containers are de-duped

This commit adds a unit test to check that the Quilt JS library
doens't return a deployment with duplicated containers if the
same container is referenced from multiple services.

kklin/quilt,LuiseV/quilt,ejj/quilt-dev,LuiseV/quilt,kayousterhout/quilt,kelda/kelda,kklin/quilt,ejj/quilt-dev,quilt/quilt,ejj/quilt-dev,kayousterhout/quilt,kklin/quilt,kklin/kelda,NetSys/quilt,quilt/quilt,NetSys/quilt,NetSys/quilt,kklin/kelda,quilt/quilt,kayousterhout/quilt,kklin/kelda,kklin/quilt,LuiseV/quilt,ejj/quilt-dev,LuiseV/quilt,kklin/kelda,LuiseV/quilt,NetSys/quilt,kayousterhout/quilt,quilt/quilt,NetSys/quilt,kelda/kelda,kelda/kelda,kelda/kelda