'virsh help | grep nodedev-det' shows only nodedev-detach, but
'virsh help nodedev | grep nodedev-det' also shows the old alias
nodedev-dettach that we intentionally hid in commit af3f9aab.
See also commit 787f4fe and this bug report:
https://bugzilla.redhat.com/show_bug.cgi?id=956966
* tools/virsh.c (vshCmdGrpHelp): Copy suppression of vshCmdHelp.
Signed-off-by: Eric Blake <eblake@redhat.com>