Bug #34454572 : Clone_persist_gtid causes memory leak

Description:
============
The Clone_persist_gtid thread causes memory leak.

Analysis:
=========
The Clone_persist_gtid thread that runs in the background write GTIDs
periodically to disk table. In this process, the thd allocates memory
to store the information about the tables to be locked while flushing
GTIDs. This memory is not freed until the shutdown is called, causing
the memory consumption or slow memory leak.

Fix:
====
Release the memory that was allocated by calling the ClearForReuse()
after the GTIDs are flushed in each cycle.

Change-Id: Ib28a2c5134b5d223c48224916911199f260f52b5

Author: TharunSai

storage/innobase/clone/clone0repl.cc

@@ -610,6 +610,12 @@ void Clone_persist_gtid::periodic_write() {
     os_event_reset(m_event);
     /* Write accumulated GTIDs to disk table */
     flush_gtids(thd);
+    /* Memory is allocated from thd->memroot to store the information about the
+    table being locked for flushing gtids. In this case, being a background
+    thread which is flushing the gtids every 100 millisecond, we should release
+    the memory after every cycle of flushing gtids to avoid memory growth in
+    Clone_persist_gtid thread .*/
+    thd->mem_root->ClearForReuse();
   }
 
   /* For slow shutdown, consume remaining GTIDs so that undo can be purged. */