Problem:
========
- InnoDB clears the fts resource when last FTS index is being dropped
if the table has user defined FTS_DOC_ID. While creating the new fts
index, InnoDB expects to have FTS resources.
Fix:
===
fts_drop_index(): Removed the fts resource clear.
fts_clear_all(): Clear the fts resource when there are no new fts
index to be added.
commit_cache_norebuild(), row_merge_drop_indexes():
Tries to call fts resource after removing associated fts index
from table object
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