fix misleading log message in ReplicationCoordinatorImpl::_startElectSelfIfEligibleV1()

ReplicationCoordinatorImpl::_startElectSelfIfEligibleV1() logs one of the 2 following messages just before starting an election:

• Starting an election for a priority takeover
• Starting an election, since we've seen no PRIMARY in the past ... ms

A successful step up request will also cause the second message to be logged, which can be misleading.