Ensure we only run the cadvisor/docker init in !dockerless

We do not want to run the `cadvisor/docker` init when we are using the
dockerless build tags. We can ensure this by isolating into a separate
file with the proper build tag constraints.

pkg/kubelet/cadvisor/BUILD

@@ -10,6 +10,7 @@ go_library(
     name = "go_default_library",
     srcs = [
         "cadvisor_linux.go",
+        "cadvisor_linux_docker.go",
         "cadvisor_unsupported.go",
         "cadvisor_windows.go",
         "doc.go",

pkg/kubelet/cadvisor/cadvisor_linux.go

@@ -29,7 +29,6 @@ import (
 	// Register supported container handlers.
 	_ "github.com/google/cadvisor/container/containerd/install"
 	_ "github.com/google/cadvisor/container/crio/install"
-	_ "github.com/google/cadvisor/container/docker/install"
 	_ "github.com/google/cadvisor/container/systemd/install"
 
 	// Register cloud info providers.

pkg/kubelet/cadvisor/cadvisor_linux_docker.go

@@ -0,0 +1,25 @@
+// +build linux,!dockerless
+
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package cadvisor
+
+import (
+	// We only want to perform this docker specific cadvisor init when we are not
+	// using the `dockerless` build tag.
+	_ "github.com/google/cadvisor/container/docker/install"
+)