[Bugfix] Issue #45 Issue #577 InnoDB crash when master thread evict dict_table_t object

Problem

================

The innodb will crash when master thread wants to evict an unused object.

The backtrace:

  ut_ad(dict_index_is_clust(index))

  row_merge_drop_indexes

  dict_table_remove_from_cache_low

  dict_make_room_in_cache ()

  srv_master_evict_from_table_cache ()

  srv_master_do_idle_tasks ()

  srv_master_thread (arg=0x0)

  start_thread (arg=0x2b21c8200700)

  clone ()

Solution

================

The wrong position of judgement logic code about variable 'drop_aborted' in function

dict_table_close() may be the root cause.

We simply move this piece of codes prior to the decrement of

table->n_ref_count, thus aborted index will be discard when this table

is being closed.