PR: 1731 and maybe 2197

Clear error queue in a few places in SSL code where errors are expected
so they don't stay in the queue.

ssl/d1_both.c

@@ -886,6 +886,8 @@ unsigned long dtls1_output_cert_chain(SSL *s, X509 *x)
   			}
   
 		X509_verify_cert(&xs_ctx);
+		/* Don't leave errors in the queue */
+		ERR_clear_error();
 		for (i=0; i < sk_X509_num(xs_ctx.chain); i++)
   			{
 			x = sk_X509_value(xs_ctx.chain, i);

ssl/s3_both.c

@@ -352,6 +352,8 @@ unsigned long ssl3_output_cert_chain(SSL *s, X509 *x)
 				return(0);
 				}
 			X509_verify_cert(&xs_ctx);
+			/* Don't leave errors in the queue */
+			ERR_clear_error();
 			for (i=0; i < sk_X509_num(xs_ctx.chain); i++)
 				{
 				x = sk_X509_value(xs_ctx.chain, i);

ssl/ssl_cert.c

@@ -755,6 +755,8 @@ int SSL_add_file_cert_subjects_to_stack(STACK_OF(X509_NAME) *stack,
 			sk_X509_NAME_push(stack,xn);
 		}
 
+	ERR_clear_error();
+
 	if (0)
 		{
 err: