docker '' causes a golang crash.

This patch fixes the problem.

Docker-DCO-1.1-Signed-off-by: Daniel Walsh <dwalsh@redhat.com> (github: rhatdan)
Merge pull request #5916 from rhatdan/crash

docker '' causes a golang crash.
Update lxc requirement to 1.0
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #5945 from crosbymichael/lxc-version-bump

Update LXC requirement to 1.0