*: validate rootfs default and verification

First of all, it doesn't make sense for us to not include a rootfs in
our default configuration -- as it means that we're providing an
invalid configuration.

Second of all, the test to check whether the path is "rootfs" is
completely meaningless. containerd and Docker would fail that test,
simply because it's pointlessly restrictive. No aspect of the
runtime-spec states that it is a spec violation to *not* use "rootfs",
so why would we punish people for it?

Fix both of these bugs.

Signed-off-by: Aleksa Sarai <asarai@suse.de>

generate/generate.go

@@ -41,7 +41,7 @@ func New() Generator {
 	spec := rspec.Spec{
 		Version: rspec.Version,
 		Root: &rspec.Root{
-			Path:     "",
+			Path:     "rootfs",
 			Readonly: false,
 		},
 		Process: &rspec.Process{

validate/validate.go

@@ -206,11 +206,6 @@ func (v *Validator) CheckRoot() (errs error) {
 		return
 	}
 
-	if filepath.Base(v.spec.Root.Path) != "rootfs" {
-		errs = multierror.Append(errs,
-			specerror.NewError(specerror.PathName, fmt.Errorf("path name should be the conventional 'rootfs'"), rspec.Version))
-	}
-
 	var rootfsPath string
 	var absRootPath string
 	if filepath.IsAbs(v.spec.Root.Path) {