Not use reset in the test

Mockito does not handle threading problem very well. Mockito
may still handle the mocking object even when it's reset and
starting to mock other staff. This commit updates the flaky
test to not to use reset instead of verify the exact
interactions of the target method.

Test: atest NetworkStackTests and verify in the test server
Bug: 286701584
Change-Id: I7b4dda9c41da9464e15044930b10dc8a3e298cae