runtime/v2: manager supports server interceptor

Currently, the runc shimv2 commandline manager doesn't support ttrpc
server's customized option, for example, the ttrpc server interceptor.
This commit is to allow the task plugin can return the
`UnaryServerInterceptor` option to the manager so that the task plugin
can do enhancement before handling the incoming request, like API-level
failpoint control.

Signed-off-by: Wei Fu <fuweid89@gmail.com>

runtime/v2/shim/shim_linux.go

@@ -21,8 +21,9 @@ import (
 	"github.com/containerd/ttrpc"
 )
 
-func newServer() (*ttrpc.Server, error) {
-	return ttrpc.NewServer(ttrpc.WithServerHandshaker(ttrpc.UnixSocketRequireSameUser()))
+func newServer(opts ...ttrpc.ServerOpt) (*ttrpc.Server, error) {
+	opts = append(opts, ttrpc.WithServerHandshaker(ttrpc.UnixSocketRequireSameUser()))
+	return ttrpc.NewServer(opts...)
 }
 
 func subreaper() error {