[cri] add sandbox and container latency metrics

These are simple metrics that allow users to view more fine grained metrics on
internal operations.

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

pkg/cri/server/container_list.go

@@ -17,6 +17,8 @@
 package server
 
 import (
+	"time"
+
 	"golang.org/x/net/context"
 
 	runtime "k8s.io/cri-api/pkg/apis/runtime/v1"
@@ -26,6 +28,7 @@ import (
 
 // ListContainers lists all containers matching the filter.
 func (c *criService) ListContainers(ctx context.Context, r *runtime.ListContainersRequest) (*runtime.ListContainersResponse, error) {
+	start := time.Now()
 	// List all containers from store.
 	containersInStore := c.containerStore.List()
 
@@ -35,6 +38,8 @@ func (c *criService) ListContainers(ctx context.Context, r *runtime.ListContaine
 	}
 
 	containers = c.filterCRIContainers(containers, r.GetFilter())
+
+	containerListTimer.UpdateSince(start)
 	return &runtime.ListContainersResponse{Containers: containers}, nil
 }