Fix ssl3_get_cert_verify key type checks.

EVP_PKT_SIGN is redundant with the RSA/EC check which, in turn, is
redundant with sigalgs processing. The type need only be checked in the
pre-1.2 case which was indeed missing an else.

The client half was likewise missing an else, though it's unreachable
due to leaf cert checks.

Change-Id: Ib3550f71a2120b38eacdd671d4f1700876bcc485
Reviewed-on: https://boringssl-review.googlesource.com/8779
Reviewed-by: David Benjamin <davidben@google.com>
diff --git a/ssl/handshake_client.c b/ssl/handshake_client.c
index 267e164..34681d3 100644
--- a/ssl/handshake_client.c
+++ b/ssl/handshake_client.c
@@ -1269,6 +1269,10 @@
       signature_algorithm = SSL_SIGN_RSA_PKCS1_MD5_SHA1;
     } else if (pkey->type == EVP_PKEY_EC) {
       signature_algorithm = SSL_SIGN_ECDSA_SHA1;
+    } else {
+      al = SSL_AD_UNSUPPORTED_CERTIFICATE;
+      OPENSSL_PUT_ERROR(SSL, SSL_R_PEER_ERROR_UNSUPPORTED_CERTIFICATE_TYPE);
+      goto f_err;
     }
 
     /* The last field in |server_key_exchange| is the signature. */