Adjust KeyAttestation test for RKP

StrongBox tests required every intermediate cert in the attestation
chain to contain "strongbox" in the subject, but this isn't the case
for RKP-issued chains.

This changes the test to require at least one cert with "strongbox".

Bug: 234395804
Test: CtsKeystoreTestCases
Change-Id: I28e7e3d345929853b8fc90fd57021758bb739e03
1 file changed