Fix for premature BLE RPA timeout

RPA timeout expires prematurely when multiple FindMe server
instances start and stop advertisiment continuously. During start
adv TIMER3 is started using oneshot timer and during stop adv
same TIMER0 is stopped, so the TIMER3 is still running and expires
prematurely. This fix stops TIMER3 during disable adv and when RPA
is sent to controller.

Change-Id: I336f84043e5e0e8a833cc6080f8bcc0c1665893e