Bluetooth: Fix memory leaks from discovery filter UUID list

In case of failure or when unplugging a controller, the allocated
memory for the UUID list of the discovery filter is not freed. Use
the newly introduced helper for reset the discovery filter and with
that also freeing existing memory.

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