 dockerfile: fix unpacking of containerd binaries
 dockerfile: fix unpacking of containerd binaries

it turns out that within the tarball, everything sits under `bin/`,
thus, we were creating

	/usr/local/concourse/bin/bin/containerd ...

by using `strip-components=1` we're able to remove that top-level `bin`
coming from the containerd tarball.

Signed-off-by: Ciro S. Costa <4f5054ab2db051d03adf9068233a850c82b24437@pivotal.io>

concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse