test/helpers: Fix retry condition for CiliumExecContext

Previously, 11cb4d0 assumed that 137 was the exit code for when a
process exists due to a SIGKILL. However, upon reading the Go source
code as of 1.20 rc1, this is not the case, and that -1 is set for all
exit codes due to signals [1].

Fixes: 11cb4d0 ("test: Keep trying exec if killed")
Fixes: cilium#22570

[1]:
https://github.com/golang/go/blob/go1.20rc1/src/os/exec_posix.go#L128-L130

Signed-off-by: Chris Tarazi <chris@isovalent.com>

test/helpers/kubectl.go

@@ -2866,15 +2866,17 @@ func (kub *Kubectl) CiliumExecContext(ctx context.Context, pod string, cmd strin
 	// avoid Kubectl issue.
 	// https://github.com/openshift/origin/issues/16246
 	//
-	// Sometimes kubectl returns 137 exit code, when the command has been
-	// killed with the stderr "signal: killed", where the same command
-	// succeeds in a forthcoming sysdump. Keep trying also in this case
-	// until the 'limitTimes' retries has been exhausted.
+	// Sometimes kubectl returns -1 exit code, when the command has been killed
+	// with the stderr "signal: killed" (or generically when a process has been
+	// killed by a signal [1]), where the same command succeeds in a
+	// forthcoming sysdump. Keep trying also in this case until the
+	// 'limitTimes' retries has been exhausted.
 	// https://github.com/cilium/cilium/issues/22476
+	// [1]: https://github.com/golang/go/blob/go1.20rc1/src/os/exec_posix.go#L128-L130
 	for i := 0; i < limitTimes; i++ {
 		res = execute()
 		switch res.GetExitCode() {
-		case 126, 137:
+		case -1, 126:
 			// Retry.
 		default:
 			kub.Logger().Warningf("command terminated with exit code %d on try %d", res.GetExitCode(), i)