Automatic merge from submit-queue
Fix build break on non-Linux OS introduced in 87aaf4c0
**What this PR does / why we need it**: simple fix for build breakage on non-Linux OS.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, #<issue_number>, ...)` format, will close that issue when PR gets merged)*:
**Special notes for your reviewer**:
```console
+++ [1102 11:16:58] linux/amd64: go build started
+++ [1102 11:20:11] linux/amd64: go build finished
+++ [1102 11:16:58] darwin/amd64: go build started
# k8s.io/kubernetes/pkg/kubelet/dockershim/cm
pkg/kubelet/dockershim/cm/container_manager_unsupported.go:33: undefined: fmt in fmt.Errorf
+++ [1102 11:16:58] windows/amd64: go build started
# k8s.io/kubernetes/pkg/kubelet/dockershim/cm
pkg/kubelet/dockershim/cm/container_manager_unsupported.go:33: undefined: fmt in fmt.Errorf
Makefile:79: recipe for target 'all' failed
make[1]: *** [all] Error 1
Makefile:255: recipe for target 'cross' failed
make: *** [cross] Error 1
Makefile:239: recipe for target 'release' failed
make: *** [release] Error 1
```
**Release note**:
```release-note
NONE
```
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