This patch fixes the following issues to make Google Chrome happy:
1. Adds CTAP_CBOR_CRED_MGMT(0x0A) which is an alias to CTAP_CBOR_CRED_MGMT_PRE(0x41)
2. Returns success instead of NO_CREDENTIALS when there are no RKs
3. Skip the "icon" property if it's empty
Tested with Google Chrome Version 80.0.3987.149