Don't reset Delayed_insert_threads on FLUSH STATUS

Docs/manual.texi

@@ -46929,6 +46929,8 @@ not yet 100% confident in this code.
 @appendixsubsec Changes in release 3.23.53
 @itemize @bullet
 @item
+Fixed that @code{SHOW STATUS} doesn't reset @code{Delayed_insert_threads}.
+@item
 Fixed core dump bug when using the @code{BINARY} cast on a @code{NULL} value.
 @item
 Fixed race condition when someone did a @code{GRANT} at the same time a new

sql/mysqld.cc

@@ -3182,7 +3182,7 @@ struct show_var_st status_vars[]= {
   {"Created_tmp_disk_tables",  (char*) &created_tmp_disk_tables,SHOW_LONG},
   {"Created_tmp_tables",       (char*) &created_tmp_tables,     SHOW_LONG},
   {"Created_tmp_files",	       (char*) &my_tmp_file_created,	SHOW_LONG},
-  {"Delayed_insert_threads",   (char*) &delayed_insert_threads, SHOW_LONG},
+  {"Delayed_insert_threads",   (char*) &delayed_insert_threads, SHOW_LONG_CONST},
   {"Delayed_writes",           (char*) &delayed_insert_writes,  SHOW_LONG},
   {"Delayed_errors",           (char*) &delayed_insert_errors,  SHOW_LONG},
   {"Flush_commands",           (char*) &refresh_version,        SHOW_LONG_CONST},