The USER operation affects all docker commands after it. This causes a
problem with our {{ include_footer }} implementation since commands in
that footer may require elevated permissions to perform.
In the current implementation I can no longer remove my proxy settings
once the USER has been changed.
Change-Id: I9b2bab5a15f595f6d52a46c64ddf59ba5608b938
Partially-Implements: blueprint drop-root
ea9d5cd067