core_Auth_Process_TargetedID: Fix creation of eduPersonTargetetdID attribute.

When using the 'attribute' option on the core:TargetedID-filter, the
resulting attribute would always contain the same value. This patch
fixes that.

Patch by José Alfonso.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@1713 44740490-163a-0410-bde0-09ae8108e29a