Handle referral realm in kprop client principal

Handle referral realm in kprop client principal

kprop uses krb5_sname_to_principal() to determine its client
principal.  If the local hostname cannot be mapped to a realm based on
the profile's domain_realm section, krb5_sname_to_principal() will (as
of 1.6) return a principal with the referral realm (""), which does
not work in a client principal.  Handle this by substituting the
default realm.

ticket: 6819
target_version: 1.9
tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@24518 dc483132-0cff-0310-8789-dd5450dbe970