vm/adb: don't check for ret code on adb shell reboot

Prevent the fuzzer from entering in an infinte loop
of device reboots when the adb shell reboot command
returns with an error code.

Fixes: #6598
Signed-off-by: Sebastian Ene <sebastianene@google.com>

Author: Sebastian Ene

vm/adb/adb.go

@@ -9,6 +9,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -390,8 +391,16 @@ func (inst *instance) repair() error {
 	// reliable solution can be sought out.
 	if inst.cfg.TargetReboot {
 		if _, err := inst.adb("shell", "reboot"); err != nil {
-			return err
+			var verboseErr *osutil.VerboseError
+			if !errors.As(err, &verboseErr) {
+				return err
+			}
+
+			if verboseErr.ExitCode != 0 && verboseErr.ExitCode != 255 {
+				return err
+			}
 		}
+
 		// Now give it another 5 minutes to boot.
 		if !vmimpl.SleepInterruptible(10 * time.Second) {
 			return fmt.Errorf("shutdown in progress")