Return correct public key for Verified Access

For key_type == KEY_DEVICE the key_name_ is empty that causes
stable device public key to be returned. To return public key for
the newly generated key pair, key_name_for_spkac_ should be used
instead.

Bug: 1045895
Change-Id: I5fd16b4605a16aefa8e48394f86d6a99e51eb6e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2157070Reviewed-by: Pavol Marko <pmarko@chromium.org>
Commit-Queue: Michael Ershov <miersh@google.com>
Cr-Commit-Position: refs/heads/master@{#760546}

chrome/browser/chromeos/attestation/tpm_challenge_key_subtle.cc

@@ -476,7 +476,7 @@ void TpmChallengeKeySubtleImpl::GetPublicKey() {
   CryptohomeClient::Get()->TpmAttestationGetPublicKey(
       key_type_,
       cryptohome::CreateAccountIdentifierFromAccountId(GetAccountId()),
-      key_name_,
+      GetKeyNameForRegister(),
       base::BindOnce(&TpmChallengeKeySubtleImpl::PrepareKeyFinished,
                      weak_factory_.GetWeakPtr()));
 }