The issue was that the value of MARIA_FOUND_WRONG_KEY was a value
that could be returned by ha_key_cmp.

This was already fixed in MyISAM, now using the same fix in Aria:
Setting the value to INT_MAX32, which should be impossible in any
normal cases.

I also fixed so that if there is a wrong key, we now get a proper error
message and not an assert.