Bluetooth: host: Fix LE SC OOB authentication and id for central role

If the application has used bt_le_oob_get_local to retrieve the OOB
RPA address and OOB authentication information the central role should
use this RPA address for the next RPA timeout period.

The central role always refreshes the RPA address for the initiator,
this will make the OOB information not usable as the peer cannot
recognize the central role since the RPA address is changed.
Check if the initiator can use the address for the duration of the of
remaining RPA period.

Fix central role using the advertiser identity when setting the private
address. The central role should only use the default identity.

Regressions from:
fbe3285b
and
4876a8f3

Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>