Problem:
When FTS index is added into a table which doesn't have 'FTS_DOC_ID'
column, Innodb rebuilds table to add column 'FTS_DOC_ID'. when this FTS
index is dropped from this table. Innodb doesn't not rebuild table to
remove 'FTS_DOC_ID' column and deletes FTS index auxiliary tables.
But it doesn't delete FTS common auxiliary tables.
Later when the database having this table is renamed, FTS auxiliary
tables are not renamed because table's flags2 (dict_table_t.flags2)
has been resetted for DICT_TF2_FTS flag during FTS index drop operation.
Now when we drop old database, it leads to an assert.

Fix:
During renaming of FTS auxiliary tables, ORed a condition to check if
table has DICT_TF2_FTS_HAS_DOC_ID flag set.

RB: 18769
Reviewed by : Jimmy.Yang@oracle.com