Problem:
As part of bug #24938374 fix, dict_operation_lock was not taken by
fts_optimize_thread while syncing fts cache.
Due to this change, alter query is able to update SYS_TABLE rows
simultaneously. Now when fts_optimizer_thread goes open index table,
It doesn't open index table if the record corresponding to that table is
set to REC_INFO_DELETED_FLAG in SYS_TABLES and hits an assert.

Fix:
If fts sync is already in progress, Alter query would wait for sync to
complete before renaming table.

RB: #19604
Reviewed by : Jimmy.Yang@oracle.com