Restore fallback non-referral TGS request to same realm

Restore fallback non-referral TGS request to same realm

MIT krb5 1.2 and earlier KDCs reject TGS requests if the canonicalize
bit is set.  Prior to 1.9, we used to handle this by making a
non-referral fallback request on any error, but the rewrite in 1.9
mistakenly changed the behavior so that fallback requests are only
made if the original request used the referral realm and the fallback
realm is different from the default realm.  Restore the old behavior.

ticket: 6917
target_version: 1.9.2
tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@24946 dc483132-0cff-0310-8789-dd5450dbe970