Fix error insert to have deterministic errno (fixes test failure on mac).

mysql-test/suite/binlog/r/binlog_ioerr.result

@@ -4,9 +4,9 @@ CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=innodb;
 INSERT INTO t1 VALUES(0);
 SET SESSION debug='+d,fail_binlog_write_1';
 INSERT INTO t1 VALUES(1);
-ERROR HY000: Error writing file 'master-bin' (errno: 22)
+ERROR HY000: Error writing file 'master-bin' (errno: 28)
 INSERT INTO t1 VALUES(2);
-ERROR HY000: Error writing file 'master-bin' (errno: 22)
+ERROR HY000: Error writing file 'master-bin' (errno: 28)
 SET SESSION debug='';
 INSERT INTO t1 VALUES(3);
 SELECT * FROM t1;

sql/log.cc

@@ -4772,7 +4772,8 @@ int MYSQL_BIN_LOG::write_cache(IO_CACHE *cache)
     }
 
     /* Write data to the binary log file */
-    DBUG_EXECUTE_IF("fail_binlog_write_1", return ER_ERROR_ON_WRITE;);
+    DBUG_EXECUTE_IF("fail_binlog_write_1",
+                    errno= 28; return ER_ERROR_ON_WRITE;);
     if (my_b_write(&log_file, cache->read_pos, length))
       return ER_ERROR_ON_WRITE;
     cache->read_pos=cache->read_end;		// Mark buffer used up