runsc/cmd: fix kill signal parsing

Signal is arg 1, not 2.
Killing with SIGABRT is useful to get Go traces.

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>

Change-Id: I0b78e34a9de3fb3385108e26fdb4ff6e9347aeff
PiperOrigin-RevId: 200742743

runsc/cmd/kill.go

@@ -72,7 +72,7 @@ func (*Kill) Execute(_ context.Context, f *flag.FlagSet, args ...interface{}) su
 	// The OCI command-line spec says that the signal should be specified
 	// via a flag, but runc (and things that call runc) pass it as an
 	// argument.
-	signal := f.Arg(2)
+	signal := f.Arg(1)
 	if signal == "" {
 		signal = "TERM"
 	}