There are two bugs related to failed ADD INDEX and
the InnoDB table cache eviction.

dict_table_close(): Try dropping failed ADD INDEX when releasing
the last table handle, not when releasing the last-but-one.

dict_table_remove_from_cache_low(): Do not invoke
row_merge_drop_indexes() after freeing all index metadata.
Instead, directly invoke row_merge_drop_indexes_dict() to
remove the metadata from the persistent data dictionary
and to free the index pages.