check table->file->inited to catch incorrect calling sequence.


mysql-test/r/innodb_handler.result:
  bug#5373: handler READ NEXT w/o HANDLER READ [FIRST]
mysql-test/t/innodb_handler.test:
  bug#5373: handler READ NEXT w/o HANDLER READ [FIRST]
sql/sql_handler.cc:
  cleanup: call index_init *correctly*, not every time.
  check table->file->inited to catch incorrect calling sequence.