Fix Vts VUR test case.

It is not guaranteed that VHAL will send the initial value event
if VUR is on. In fact, car property service explicitly calls getValue
to generate the initial value event. Hence, if VUR is on, our test
case should allow situation where no event is generated.

Test: atest VtsHalAutomotiveVehicle_TargetTest
Bug: 334803613
Change-Id: Id924fdd2a407b1a076102c4dd57efc6043cde359