Simplified and made more determenistic myisam_crash_before_flush_keys
test.

mysql-test/r/myisam_crash_before_flush_keys.result:
  We don't need myisamchk to test this bug fix. CHECK TABLE
  after server restart is enough to ensure that the fix
  works.
mysql-test/t/myisam_crash_before_flush_keys.test:
  We don't need myisamchk to test this bug fix. CHECK TABLE
  after server restart is enough to ensure that the fix
  works.