Bluetooth: tester: Change RPA timeout

This changes RPA timeout so that the address is changed every 60
seconds. This change is needed to speed up privacy related test cases.
Currently, the new RPA was initiated on request that was a bit hackish
and could be done via BT_RPA_TIMEOUT Kconfig option.

Signed-off-by: Mariusz Skamra <mariusz.skamra@codecoup.pl>