tests/docker.userns: Set SELinux to permissive mode
tests/docker.userns: Set SELinux to permissive mode

A docker bug causes the docker daemon to fail in creating a container
when the '--userns-remap' option is used and SELinux is enforcing.
Set SELinux to permisive mode so this test can run.
See: https://github.com/opencontainers/runc/pull/1562 (nsenter:
improve namespace creation and SELinux IPC handling).

Fixes runtime errors like these:

  OCI runtime create failed: running exec setns process for init caused exit

Signed-off-by: Geoff Levand <c3918f39022407dee6a0056ceca9b1aa80e8e4ce@infradead.org>

glevand/coreos--mantle,glevand/coreos--mantle