Ignoring error codes from type conversion allows default (wrong) values to
 go unnoticed in the formation of index search conditions.
 Fixed by correctly checking for conversion errors.


mysql-test/r/select.result:
  Bug #22344: InnoDB keys act strange on datetime vs timestamp comparison
   - test case
mysql-test/t/select.test:
  Bug #22344: InnoDB keys act strange on datetime vs timestamp comparison
   - test case
sql/field.h:
  Bug #22344: InnoDB keys act strange on datetime vs timestamp comparison
   - don't ignore coversion errors
sql/field_conv.cc:
  Bug #22344: InnoDB keys act strange on datetime vs timestamp comparison
   - don't ignore coversion errors
sql/item.cc:
  Bug #22344: InnoDB keys act strange on datetime vs timestamp comparison
   - don't ignore coversion errors