Fix iprop with fallback

Fix iprop with fallback

kpropd produces a client principal name with
krb5_sname_to_principal(), then converts it to a string to pass as the
client principal to kadm5_init_with_skey().  This conversion loses the
name type, so no canonicalization is performed by libkadm5.

Commit dcb79089276624d7ddf44e08d35bd6d7d7e557d2 addresses this problem
for kadmin -k by looking for the referral realm, but kpropd sets the
realm in the krb5_sname_to_principal() result.  Add an additional
check for a two-component principal with kiprop as the first
component.

(cherry picked from commit cd61bdcd6339b10e6cf3feb9f6cb369213e8d7fc)

ticket: 9056
version_fixed: 1.20