Skipping test on GSI + first_api_level < U

The test is marked as assumption failed for Key attestation fails on the
combination of the build with the vendor froze on the Android T base
build and Android U/V GSI build because the attestation properties
ro.product.*_for_attestation have to be present in vendor properties
files.

Bug: 396582186
Test:
VtsAidlKeyMintTargetTest.PerInstance/NewKeyGenerationTest

Change-Id: I661fb0041b6e8918a32f6ee72024ebad119260d0
Merged-In: I661fb0041b6e8918a32f6ee72024ebad119260d0