Cleanup glide (#1353)

* Cleanup mentions about glide

* Don't use glide to ignore vendor directory

Since go-1.9, "./..." no longer contains the "vendor" directory.
Also, since #1305 migrated dependency management from glide to go mod,
there is no need to think about the "vendor" directory.

See: https://golang.org/doc/go1.9#vendor-dotdotdot

* go mod tidy

go.mod

@@ -17,7 +17,6 @@ replace github.com/containerd/containerd => github.com/containerd/containerd v1.
 replace golang.org/x/sys => golang.org/x/sys v0.0.0-20201029080932-201ba4db2418
 
 require (
-	github.com/Nvveen/Gotty v0.0.0-20120604004816-cd527374f1e5 // indirect
 	github.com/docker/cli v0.0.0-20190711175710-5b38d82aa076
 	github.com/docker/go-connections v0.4.0
 	github.com/docker/libcompose v0.4.0
@@ -25,23 +24,18 @@ require (
 	github.com/fsouza/go-dockerclient v1.6.5
 	github.com/google/go-cmp v0.4.0
 	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 // indirect
-	github.com/gotestyourself/gotestyourself v2.2.0+incompatible // indirect
 	github.com/imdario/mergo v0.3.10 // indirect
 	github.com/joho/godotenv v1.3.0
-	github.com/mattn/goveralls v0.0.7 // indirect
-	github.com/mitchellh/gox v1.0.1 // indirect
 	github.com/moby/sys/mount v0.1.1 // indirect
 	github.com/moby/term v0.0.0-20200915141129-7f0af18e79f2 // indirect
-	github.com/modocache/gover v0.0.0-20171022184752-b58185e213c5 // indirect
 	github.com/novln/docker-parser v1.0.0
-	github.com/opencontainers/selinux v1.6.0 // indirect
 	github.com/openshift/api v0.0.0-20200803131051-87466835fcc0
 	github.com/pkg/errors v0.9.1
 	github.com/sirupsen/logrus v1.6.0
 	github.com/spf13/cast v1.3.1
 	github.com/spf13/cobra v1.0.0
 	github.com/spf13/viper v1.7.1
-	golang.org/x/lint v0.0.0-20200302205851-738671d3881b // indirect
+	golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e // indirect
 	gopkg.in/yaml.v2 v2.3.0
 	gopkg.in/yaml.v3 v3.0.0-20200615113413-eeeca48fe776
 	gotest.tools/v3 v3.0.3 // indirect