LVS Key Suggestor does not return trust anchor

[tianyuan129]

The highlighted piece of code avoids returning all self-signed certificates.

# This is to avoid self-signed certificate
if (not cert.signature_info or not cert.signature_info.key_locator
        or not cert.signature_info.key_locator.name):
    continue

If trust anchor is in the keychain, the key suggestor never returns it even if it's a valid signer.