in the pagecache: fixing wrong assertion and a test case.
maria.test and ps_maria.test still fail.


mysql-test/r/maria.result:
  result update
mysql-test/t/maria.test:
  added test for incorrect assert on page's type
storage/maria/ma_pagecache.c:
  It is allowed to change unknown type to any legal type of page in the
  pagecache.