Fixing a race condition while collecting the engine independent statistics.

Thread1>
1) start running "ANALYZE TABLE t PERISTENT FOR COLUMNS (..) INDEXES ($list)"
2) Walk through $list and save it in TABLE::keys_in_use_for_query
3) Close/re-open tables

Thread2>
1) Make some use of table t. This involves taking table t from
   the table cache, and putting it back (with TABLE::keys_in_use_for_query reset to 0)

Thread1>
continue collecting EITS stats. Since TABLE::keys_in_use_for_query is set to 0 we
will not collect statistics for indexes in $list.