use a const metric for build_info

Signed-off-by: Michael Crosby <michael@thepasture.io>

cmd/containerd/command/main.go

@@ -30,7 +30,7 @@ import (
 	"github.com/containerd/containerd/defaults"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/log"
-	"github.com/containerd/containerd/metrics"
+	_ "github.com/containerd/containerd/metrics" // import containerd build info
 	"github.com/containerd/containerd/mount"
 	"github.com/containerd/containerd/services/server"
 	srvconfig "github.com/containerd/containerd/services/server/config"
@@ -219,7 +219,6 @@ can be used and modified as necessary as a custom configuration.`
 			serve(ctx, l, server.ServeDebug)
 		}
 		if config.Metrics.Address != "" {
-			metrics.Register()
 			l, err := net.Listen("tcp", config.Metrics.Address)
 			if err != nil {
 				return errors.Wrapf(err, "failed to get listener for metrics endpoint")