Problem:
=======
 InnoDB allows virtual index to be referenced index in foreign key
relations. While dropping the virtual column, Inplace alter does
allow the table to be closed and open it using table name to
update dict_table_t::v_cols. While loading the table, it doesn't
allow any error to be ignored. InnoDB can't find the referenced
virtual index and fails to load the table during Inplace alter.

Solution:
=========
  During inplace alter, ignore the foreign key error while loading
the table.

Reviewed-by: Marko Mäkelä