WITH INCORRECT KEY NAME

Problem:
=======
The duplicate key error of online alter report a incorrect key name. It
always report PRIMARY KEY as the duplicate key even though the PK doesn't
have duplicate key.

Solution:
========
Report the correct index name when there is a duplicate key error during
online alter operation.

Reviewed-by: Marko Mäkelä <marko.makela@oracle.com>
RB: 10125