bluetooth: host: Fix uninitialized own_addr_type for legacy scan+adv

In 25c993e5 a new case was introduced
where own_addr_type is not set by bt_id_set_scan_own_addr properly.

This led to issues for users where increasing their zephyr version
led to failures to start scanning after advertising in the case where
CONFIG_BT_SCAN_WITH_IDENTITY=n and legacy advertising commands are used.

Signed-off-by: Olivier Lesage <olivier.lesage@nordicsemi.no>