KeyMint VTS: cope with ATTEST_KEY +/- SIGN

This change syncs aosp/master with the change in http://aosp/2117528,
allowing devices that launched with the (incorrect) version of
ATTEST_KEY VTS tests in Android S to continue to pass the test.

Bug: 197096139
Bug: 230074335
Test: VtsAidlKeyMintTargetTest
Change-Id: If88642e238e64ca9ec80303a4a72f7171c63464f
Merged-In: If88642e238e64ca9ec80303a4a72f7171c63464f
1 file changed