Debian has started building packages with usernamespaces
to disable network access and similar isolation features. The
containerd package executes a unit test that fails in that
scenario, see https://bugs.debian.org/1070411
The code contains a conditional on whether it is running in
usernamepsace. This commit expands the unit test to cover
this behavior; it was previously untested.
The easiest way to reproduce this issue is to prefix the test
invocaiton with 'unshare -nr go test [...]'
Signed-off-by: Reinhard Tartler <siretart@gmail.com>