Remove Alpha feature Mount Containers

The alpha feature for mount containers is unused, and is
superseded by CSI. By removing it, we can remove a lot of unnecessary
code, and also clean up the mount library even more before moving it out
of tree.

Author: codenrhoden

pkg/features/kube_features.go

@@ -183,12 +183,6 @@ const (
 	// Enable nodes to exclude themselves from network disruption checks
 	NodeDisruptionExclusion featuregate.Feature = "NodeDisruptionExclusion"
 
-	// owner: @jsafrane
-	// alpha: v1.9
-	//
-	// Enable running mount utilities in containers.
-	MountContainers featuregate.Feature = "MountContainers"
-
 	// owner: @saad-ali
 	// alpha: v1.12
 	// beta:  v1.14
@@ -532,7 +526,6 @@ var defaultKubernetesFeatureGates = map[featuregate.Feature]featuregate.FeatureS
 	TopologyManager:                {Default: false, PreRelease: featuregate.Alpha},
 	ServiceNodeExclusion:           {Default: false, PreRelease: featuregate.Alpha},
 	NodeDisruptionExclusion:        {Default: false, PreRelease: featuregate.Alpha},
-	MountContainers:                {Default: false, PreRelease: featuregate.Alpha},
 	CSIDriverRegistry:              {Default: true, PreRelease: featuregate.Beta},
 	CSINodeInfo:                    {Default: true, PreRelease: featuregate.Beta},
 	BlockVolume:                    {Default: true, PreRelease: featuregate.Beta},

pkg/kubelet/BUILD

@@ -63,7 +63,6 @@ go_library(
         "//pkg/kubelet/logs:go_default_library",
         "//pkg/kubelet/metrics:go_default_library",
         "//pkg/kubelet/metrics/collectors:go_default_library",
-        "//pkg/kubelet/mountpod:go_default_library",
         "//pkg/kubelet/network/dns:go_default_library",
         "//pkg/kubelet/nodelease:go_default_library",
         "//pkg/kubelet/nodestatus:go_default_library",
@@ -109,7 +108,6 @@ go_library(
         "//pkg/volume:go_default_library",
         "//pkg/volume/csi:go_default_library",
         "//pkg/volume/util:go_default_library",
-        "//pkg/volume/util/exec:go_default_library",
         "//pkg/volume/util/hostutil:go_default_library",
         "//pkg/volume/util/subpath:go_default_library",
         "//pkg/volume/util/types:go_default_library",
@@ -293,7 +291,6 @@ filegroup(
         "//pkg/kubelet/lifecycle:all-srcs",
         "//pkg/kubelet/logs:all-srcs",
         "//pkg/kubelet/metrics:all-srcs",
-        "//pkg/kubelet/mountpod:all-srcs",
         "//pkg/kubelet/network:all-srcs",
         "//pkg/kubelet/nodelease:all-srcs",
         "//pkg/kubelet/nodestatus:all-srcs",