May also fix: MDEV-14970 "MariaDB crashed with signal 11 and Aria table"

I am not able to reproduce a crash, however there was no protection in
print_keydup_error() if the storage engine reported the wrong key number.

This patch adds such a protection and should stop any further crashes
in this case.

Other things:
- Added extra protection in Aria to not set errkey to more than number of
  keys. (Don't think this is cause of this crash, but better safe than
  sorry)
- Extend test_if_equal_repl_errors() to handle different cases of
  ER_DUP_ENTRY. This is just mainly precaution for the future.