consistent read (Bug #12669).


mysql-test/r/innodb.result:
  Added test results for a checksum test.
mysql-test/t/innodb.test:
  Added test case for a checksum bug #12669.
sql/ha_innodb.cc:
  Use consistent read for checksum table and convert MySQL lock type
  to the TL_READ because at the moment MySQL uses TL_READ_NO_INSERT.