Bug#930293: unblock: docker.io/18.09.1+dfsg1-7

[Sam Hartman]

Hi, Paul.

I can think of a number of cases why docker tests might be problematic
in our build environment.
I actually think that if these tests run in a VM  but not in a build
environment within a schroot, it's a fairly good sign that the tests
are problematic the way we do builds.
I'll try to do that right now and see what happens.