Fix algorithm_auth and SSL_k* mismatch.

Fixes bug introduced in c26c802a89. Only one of
the two halves got flipped.

Change-Id: I0b3905ab22b0f83f093e1720af85594b1a970a7f
Reviewed-on: https://boringssl-review.googlesource.com/1152
Reviewed-by: Adam Langley <agl@google.com>

ssl/s3_clnt.c

@@ -1333,7 +1333,7 @@ int ssl3_get_key_exchange(SSL *s)
 		   omitted if no identity hint is sent. Set
 		   session->sess_cert anyway to avoid problems
 		   later.*/
-		if (s->s3->tmp.new_cipher->algorithm_mkey & SSL_aPSK)
+		if (s->s3->tmp.new_cipher->algorithm_auth & SSL_aPSK)
 			{
 			s->session->sess_cert=ssl_sess_cert_new();
 			if (s->session->psk_identity_hint)