Fixed a wrong return code by the function init_key_cache.


mysys/mf_keycache.c:
  Fixed a wrong return code by the function init_key_cache.
mysql-test/t/key_cache.test:
  Fixed a wrong return code by the function init_key_cache.
mysql-test/r/key_cache.result:
  Fixed a wrong return code by the function init_key_cache.