Bluetooth: mgmt: Fix name_changed event for short name changes

Since we can't reliably track the short name changes just assume that we
had a change whenever there's a pending mgmt command. In the worst case
we just get one unnecessary name_changed signal.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>