Remove kubelet dependency on pidof

Issue #26093 identified pidof as one of the dependencies of kublet
which could be worked around. In this PR, we just look at /proc
to construct the list of pids we need for a specified process
instead of running "pidof" executable

Related to #26093

pkg/util/procfs/procfs_test.go

@@ -18,7 +18,12 @@ package procfs
 
 import (
 	"io/ioutil"
+	"os"
+	"path/filepath"
+	"runtime"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func verifyContainerName(procCgroupText, expectedName string, expectedErr bool, t *testing.T) {
@@ -56,3 +61,12 @@ func TestContainerNameFromProcCgroup(t *testing.T) {
 	procCgroupInvalid := "devices:docker/kubelet\ncpuacct:pkg/kubectl"
 	verifyContainerName(procCgroupInvalid, "", true, t)
 }
+
+func TestPidOf(t *testing.T) {
+	if runtime.GOOS == "darwin" || runtime.GOOS == "windows" {
+		t.Skipf("not supported on GOOS=%s", runtime.GOOS)
+	}
+	pids := PidOf(filepath.Base(os.Args[0]))
+	assert.NotZero(t, pids)
+	assert.Contains(t, pids, os.Getpid())
+}