pkg/fileutils: remove gotest.tools as dependency, use t.TempDir()
pkg/fileutils: remove gotest.tools as dependency, use t.TempDir()

In preparation of moving this package separate.

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>

trebonian/docker,konstruktoid/docker-upstream,mahak/docker,mahak/docker,thaJeztah/docker,jimjag/docker,Mokolea/docker,konstruktoid/docker-upstream,jimjag/docker,Mokolea/docker,cpuguy83/docker,mahak/docker,konstruktoid/docker-upstream,jimjag/docker,trebonian/docker,thaJeztah/docker,moby/moby,Mokolea/docker,thaJeztah/docker,Ramzec/docker,Mokolea/docker,Ramzec/docker,moby/moby,moby/moby,cpuguy83/docker,trebonian/docker,konstruktoid/docker-upstream,moul/docker,Ramzec/docker,mahak/docker,trebonian/docker,jimjag/docker,moul/docker,thaJeztah/docker,moby/moby,cpuguy83/docker,cpuguy83/docker,moul/docker,Ramzec/docker,moul/docker