build: Print command output in build-push
build: Print command output in build-push

For some reason we're failing to push containers on travis, and this
turns out to be impossible to debug without knowing what the build
scripts are doing.

stevenlin598/quilt,kayousterhout/quilt,PenguinToast/quilt,kklin/quilt,stevenlin598/quilt,tejasmanohar/quilt,tejasmanohar/quilt,ejj/quilt-dev,PenguinToast/quilt,ZhongtianWang/quilt,LuiseV/quilt,mmussomele/quilt,kelda/kelda,akshayknarayan/quilt,akshayknarayan/quilt,NetSys/quilt,kayousterhout/quilt,quilt/quilt,quilt/quilt,tejasmanohar/quilt,stevenlin598/quilt,ZhongtianWang/quilt,kklin/quilt,kklin/quilt,akshayknarayan/quilt,LuiseV/quilt,kelda/kelda,tejasmanohar/quilt,PenguinToast/quilt,secant/quilt,mmussomele/quilt,kklin/kelda,PenguinToast/quilt,LuiseV/quilt,secant/quilt,NetSys/quilt,quilt/quilt,ZhongtianWang/quilt,NetSys/quilt,kklin/quilt,kelda/kelda,NetSys/quilt,ejj/quilt-dev,PenguinToast/quilt,kklin/kelda,mmussomele/quilt,akshayknarayan/quilt,quilt/quilt,ejj/quilt-dev,LuiseV/quilt,stevenlin598/quilt,secant/quilt,mmussomele/quilt,secant/quilt,ZhongtianWang/quilt,LuiseV/quilt,kayousterhout/quilt,mmussomele/quilt,stevenlin598/quilt,mmussomele/quilt,kayousterhout/quilt,stevenlin598/quilt,ejj/quilt-dev,kelda/kelda,NetSys/quilt,secant/quilt,kklin/kelda,kklin/kelda