ref(builder): remove volume definition in Dockerfile

This was missed in #1917.
Merge pull request #1984 from carmstrong/remove_builder_volume

ref(builder): remove volume definition in Dockerfile
fix(builder): restore VOLUME instruction so builder does not stack overlay filesystems

fix(builder): add comment explaining dockerfile volume change
Merge pull request #1996 from gabrtv/fix-builder-volume

fix(builder): restore VOLUME instruction so builder does not stack overlay filesystems
ref(tests): update details in CI node setup script
Merge pull request #1983 from mboersma/test-setup-tweaks

ref(tests): update details in CI node setup script
feat(logspout): introduce deis/logspout