CtsVerifier: Fix Camera Formats to deal with repeated formats

Some devices include the same preview callback format multiple times
in their supported formats list; the formats test would collapse them
into one in some places, but not all. As a result, it would not allow
the test to pass after all the combinations had been tested.

Bug: 17601180
Change-Id: I87f3d20b9d4266afd3bebaabdc8ca7800751c9df