Register grpc metrics in main

This needs to be registered last after all other services have been
registred.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

services/metrics/metrics.go

@@ -1,26 +0,0 @@
-package metrics
-
-import (
-	"github.com/containerd/containerd/plugin"
-	grpc_prometheus "github.com/grpc-ecosystem/go-grpc-prometheus"
-	"google.golang.org/grpc"
-)
-
-func init() {
-	plugin.Register("metrics-grpc", &plugin.Registration{
-		Type: plugin.GRPCPlugin,
-		Init: New,
-	})
-}
-
-func New(_ *plugin.InitContext) (interface{}, error) {
-	return &Service{}, nil
-}
-
-type Service struct {
-}
-
-func (s *Service) Register(server *grpc.Server) error {
-	grpc_prometheus.Register(server)
-	return nil
-}