Fix local testing of xenial-common.
Fix local testing of xenial-common.

Make it possible for `make docker.build.xenial-common` to work locally.

appsembler/configuration,EDUlib/configuration,arbrandes/edx-configuration,mitodl/configuration,stvstnfrd/configuration,edx/configuration,mitodl/configuration,appsembler/configuration,arbrandes/edx-configuration,arbrandes/edx-configuration,EDUlib/configuration,appsembler/configuration,edx/configuration,stvstnfrd/configuration,arbrandes/edx-configuration,EDUlib/configuration,EDUlib/configuration,mitodl/configuration,edx/configuration,arbrandes/edx-configuration,EDUlib/configuration,edx/configuration,stvstnfrd/configuration,mitodl/configuration,stvstnfrd/configuration,stvstnfrd/configuration,appsembler/configuration