fix: Bring back the --all flag of kill

The shim uses the --all flag in Kubernetes settings when calling the
low level runtime. We previously removed this flag causing issues in the
deletion path of the pod. Therefore, we need to bring it back.

PR: #717
Signed-off-by: Charalampos Mainas <cmainas@nubificus.co.uk>
Reviewed-by: Anastassios Nanos <ananos@nubificus.co.uk>
Approved-by: Anastassios Nanos <ananos@nubificus.co.uk>

Author: cmainas

cmd/urunc/kill.go

@@ -41,6 +41,13 @@ For example, if the container id is "ubuntu01" the following will send a "KILL"
 signal to the init process of the "ubuntu01" container:
 
 	# urunc kill ubuntu01 KILL`,
+	Flags: []cli.Flag{
+		&cli.BoolFlag{
+			Name:    "all",
+			Aliases: []string{"a"},
+			Usage:   "send the specified signal to all processes inside the container",
+		},
+	},
 	Action: func(_ context.Context, cmd *cli.Command) error {
 		runtime.GOMAXPROCS(1)
 		runtime.LockOSThread()