Add support for kpod kill

Kill one or more containers using a user-provided signal.  If not signal
is provided, KILL is used.

Signed-off-by: baude <bbaude@redhat.com>

cmd/kpod/kill.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/docker/docker/pkg/signal"
+	"github.com/kubernetes-incubator/cri-o/libkpod"
+	"github.com/pkg/errors"
+	"github.com/urfave/cli"
+)
+
+var (
+	killFlags = []cli.Flag{
+		cli.StringFlag{
+			Name:  "signal, s",
+			Usage: "Signal to send to the container",
+			Value: "KILL",
+		},
+	}
+	killDescription = "The main process inside each container specified will be sent SIGKILL, or any signal specified with option --signal."
+	killCommand     = cli.Command{
+		Name:        "kill",
+		Usage:       "Kill one or more running containers with a specific signal",
+		Description: killDescription,
+		Flags:       killFlags,
+		Action:      killCmd,
+		ArgsUsage:   "[CONTAINER_NAME_OR_ID]",
+	}
+)
+
+// killCmd kills one or more containers with a signal
+func killCmd(c *cli.Context) error {
+	args := c.Args()
+	if len(args) == 0 {
+		return errors.Errorf("specify one or more containers to kill")
+	}
+	config, err := getConfig(c)
+	if err != nil {
+		return errors.Wrapf(err, "could not get config")
+	}
+	server, err := libkpod.New(config)
+	if err != nil {
+		return errors.Wrapf(err, "could not get container server")
+	}
+	killSignal := c.String("signal")
+	// Check if the signalString provided by the user is valid
+	// Invalid signals will return err
+	sysSignal, err := signal.ParseSignal(killSignal)
+	if err != nil {
+		return err
+	}
+	defer server.Shutdown()
+	err = server.Update()
+	if err != nil {
+		return errors.Wrapf(err, "could not update list of containers")
+	}
+	var lastError error
+	for _, container := range c.Args() {
+		id, err := server.ContainerKill(container, sysSignal)
+		if err != nil {
+			if lastError != nil {
+				fmt.Fprintln(os.Stderr, lastError)
+			}
+			lastError = errors.Wrapf(err, "unable to kill %v", container)
+		} else {
+			fmt.Println(id)
+		}
+	}
+	return lastError
+}