Don't fail attestation on missing app ID

As identified by Droidguard, a non-trivial percentage of attestations
fail with a missing attestation app ID.  It's better to produce an
attestation with missing app ID than to fail, because not all
consumers of attestations care about the app ID.

Test: Keystore CTS tests.
Change-Id: I1a8d8a6873edab27771bff4ce9262f4fbe533e56
1 file changed