allow server preauth plugin verify_padata function to return e-data

allow server preauth plugin verify_padata function to return e-data

Change server-side preauth plugin interface to allow the plugin's
verify_padata function to return e-data to be returned to the client.
(Patch from Nalin Dahyabhai <nalin@redhat.com>)

Update sample plugins to return e-data to exercise the code.

Fix memory leak in the wpse plugin.

ticket: new
Component: krb5-kdc
Target_Version: 1.6
Tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@18801 dc483132-0cff-0310-8789-dd5450dbe970