VTS: Verify no duplicate entries between partial results

Partial results are appended together. If there are duplicate entries
between partial results, there will be more than more entries for a tag
in the final result. This can cause undefined behavior, especially when
they have different values.

Test: Run Camera VTS test on Pixel devices
Bug: 170575182
Change-Id: I931660cef16a90ee0c247e3c4513a88adb7211ab