Backport from the Falcon tree.

When opening/creating the transaction coordinator's log, if binlog is
used, the tc log is the binlog so we use the binlog's name; otherwise
we use the mmap-based log, named after the mandatory argument of the
--log-tc option (meant for that).

sql/log.cc

@@ -2523,7 +2523,7 @@ int TC_LOG_MMAP::open(const char *opt_name)
       goto err;
     if (using_heuristic_recover())
       return 1;
-    if ((fd= my_create(logname, O_RDWR, 0, MYF(MY_WME))) < 0)
+    if ((fd= my_create(logname, CREATE_MODE, O_RDWR, MYF(MY_WME))) < 0)
       goto err;
     inited=1;
     file_length= opt_tc_log_size;

sql/mysqld.cc

@@ -3171,7 +3171,7 @@ server.");
                                (TC_LOG *) &tc_log_mmap) :
            (TC_LOG *) &tc_log_dummy);
 
-  if (tc_log->open(opt_bin_logname))
+  if (tc_log->open(opt_bin_log ? opt_bin_logname : opt_tc_log_file))
   {
     sql_print_error("Can't init tc log");
     unireg_abort(1);