Verify at least 2 frames out of signal handler.

Modify the test slightly to make sure that the unwinder properly unwinds
through at least 2 frames outside of the signal handler. This guarantees
that if the first frame outside of the handler happens to be garbage,
this test will fail.

Bug: 34468756

Test: Ran the unit tests on fugu, angler (both 32 bit and 64 bit).
Change-Id: I6b76ac9fc1df9ed6fd5bbcc6f5fa4bf458354dff