Re-think integration vendoring

- remove docker/docker from  Traefik vendor (unused)
- use `ignore` for all Traefik vendor in integration glide.
- defined only integration specific version of the dependencies.

integration/vendor/github.com/Sirupsen/logrus/exported.go

@@ -48,11 +48,6 @@ func AddHook(hook Hook) {
 	std.Hooks.Add(hook)
 }
 
-// WithError creates an entry from the standard logger and adds an error to it, using the value defined in ErrorKey as key.
-func WithError(err error) *Entry {
-	return std.WithField(ErrorKey, err)
-}
-
 // WithField creates an entry from the standard logger and adds a field to
 // it. If you want multiple fields, use `WithFields`.
 //