Update CarEvsManagerTest#startTwoVideoStreamsAndStopThemIndividually

Accommodates test scenarios with the existence of another CarEvsService
clients that could make CarEvsService's state unchanged.

Fix: 397560309
Test: atest CarEvsManagerTest
Flag: EXEMPT bug fix
Change-Id: I56692c545bad24cda5e1ad4a9c3037bb6d76d794
1 file changed