Assume we have two trusted CAs with the same name, the first uses ECDSA 256
bits, the second RSA 2048; cert is signed by the second. If we do the keysize
check before we checked the key types match, we'll raise the badkey flags when
checking the EC-256 CA and it will remain up even when we finally find the
correct CA. So, move the check for the key size after signature verification,
which implicitly checks the key type.