Vendor Update

vendor.conf

vendor/github.com/containerd/containerd/.appveyor.yml

vendor/github.com/containerd/containerd/.gitignore

vendor/github.com/containerd/containerd/.golangci.yml

vendor/github.com/containerd/containerd/.mailmap

vendor/github.com/containerd/containerd/.travis.yml

vendor/github.com/containerd/containerd/.zuul.yaml

vendor/github.com/containerd/containerd/ADOPTERS.md

vendor/github.com/containerd/containerd/BUILDING.md

vendor/github.com/containerd/containerd/LICENSE

vendor/github.com/containerd/containerd/Makefile

vendor/github.com/containerd/containerd/Makefile.darwin

vendor/github.com/containerd/containerd/Makefile.freebsd

vendor/github.com/containerd/containerd/Makefile.linux

vendor/github.com/containerd/containerd/Makefile.windows

vendor/github.com/containerd/containerd/NOTICE

vendor/github.com/containerd/containerd/PLUGINS.md

vendor/github.com/containerd/containerd/Protobuild.toml

vendor/github.com/containerd/containerd/README.md

vendor/github.com/containerd/containerd/RELEASES.md