Fix minijail_change_{user|group} with invalid users/groups.

BUG=chromium:356736
TEST='minijail0 -u <invalid> -- /usr/bin/id' fails.
TEST='minijail0 -g <invalid> -- /usr/bin/id' fails.

Change-Id: I0e1a35f5c582060bade53edb7cfda3eb1892d83c
Reviewed-on: https://chromium-review.googlesource.com/191701
Tested-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Nam Nguyen <namnguyen@chromium.org>
Commit-Queue: Jorge Lucangeli Obes <jorgelo@chromium.org>
1 file changed