MDEV-8540 - Crash on server shutdown since 10.0.16

For the purpose of reporting an error to error log, shutdown thread was
attempting to access current_thd->variables.lc_messages->errmsgs->errmsgs.
Whereas current_thd was NULL.

We should log errors according to global lc_messages setting instead of
session setting.

sql/log.cc

@@ -2499,14 +2499,14 @@ void MYSQL_LOG::close(uint exiting)
     if (log_type == LOG_BIN && mysql_file_sync(log_file.file, MYF(MY_WME)) && ! write_error)
     {
       write_error= 1;
-      sql_print_error(ER_THD_OR_DEFAULT(current_thd, ER_ERROR_ON_WRITE), name, errno);
+      sql_print_error(ER_DEFAULT(ER_ERROR_ON_WRITE), name, errno);
     }
 
     if (!(exiting & LOG_CLOSE_DELAYED_CLOSE) &&
         mysql_file_close(log_file.file, MYF(MY_WME)) && ! write_error)
     {
       write_error= 1;
-      sql_print_error(ER_THD_OR_DEFAULT(current_thd, ER_ERROR_ON_WRITE), name, errno);
+      sql_print_error(ER_DEFAULT(ER_ERROR_ON_WRITE), name, errno);
     }
   }
 
@@ -2690,7 +2690,7 @@ bool MYSQL_QUERY_LOG::write(time_t event_time, const char *user_host,
   if (!write_error)
   {
     write_error= 1;
-    sql_print_error(ER(ER_ERROR_ON_WRITE), name, errno);
+    sql_print_error(ER_DEFAULT(ER_ERROR_ON_WRITE), name, errno);
   }
   mysql_mutex_unlock(&LOCK_log);
   return TRUE;
@@ -2866,7 +2866,7 @@ bool MYSQL_QUERY_LOG::write(THD *thd, time_t current_time,
       if (! write_error)
       {
         write_error= 1;
-        sql_print_error(ER(ER_ERROR_ON_WRITE), name, tmp_errno);
+        sql_print_error(ER_DEFAULT(ER_ERROR_ON_WRITE), name, tmp_errno);
       }
     }
   }
@@ -6385,7 +6385,7 @@ void MYSQL_BIN_LOG::close(uint exiting)
     if (mysql_file_close(index_file.file, MYF(0)) < 0 && ! write_error)
     {
       write_error= 1;
-      sql_print_error(ER(ER_ERROR_ON_WRITE), index_file_name, errno);
+      sql_print_error(ER_DEFAULT(ER_ERROR_ON_WRITE), index_file_name, errno);
     }
   }
   log_state= (exiting & LOG_CLOSE_TO_BE_OPENED) ? LOG_TO_BE_OPENED : LOG_CLOSED;