Otherwise, the script will fail.
Also add for tox invocation until potential group issue is sorted out
(group membership applied to current running shell).
Change-Id: Ic84d5435761deae0d28909c813cb1d87540fbb21
The setup_docker script downloads and starts the Docker binary while
the tox run performs the actual test of verifying all the Dockerfiles
in the project successfully builds or fails as expected.
Change-Id: I4d05c32a2faa30f0b15487dfd605089f61baf985