e2e: use SIGTERM instead of SIGINT for etcdctl tests

SIGINT needs special handling for ptys, causing some environments
to not deliver the signal. Use SIGTERM instead.

e2e/ctl_v3_elect_test.go

@@ -17,6 +17,7 @@ package e2e
 import (
 	"os"
 	"strings"
+	"syscall"
 	"testing"
 	"time"
 
@@ -77,15 +78,17 @@ func testElect(cx ctlCtx) {
 	}
 
 	// kill blocked process with clean shutdown
-	if err = blocked.Signal(os.Interrupt); err != nil {
+	// NB: this was os.Interrupt but depending on how CI is launched
+	// the SIGINT can be blocked from delivery to the etcdctl via pty.
+	if err = blocked.Signal(syscall.SIGTERM); err != nil {
 		cx.t.Fatal(err)
 	}
 	if err = closeWithTimeout(blocked, time.Second); err != nil {
 		cx.t.Fatal(err)
 	}
 
 	// kill the holder with clean shutdown
-	if err = holder.Signal(os.Interrupt); err != nil {
+	if err = holder.Signal(syscall.SIGTERM); err != nil {
 		cx.t.Fatal(err)
 	}
 	if err = closeWithTimeout(holder, time.Second); err != nil {