Simplify kdb5_ldap_util special princ creation

In kdb5_ldap_realm.c, factor out special principal creation into three
helper functions to reduce the amount of verbiage in kdb5_ldap_create.
Add kiprop/<master-hostname> during KDB creation

To reduce the number of steps in the deployment of iprop, create the
kiprop/hostname principal for the master KDC during KDB creation.
Adjust tests to match the new behavior.

[ghudson@mit.edu: clarified commit message; avoided applying kadmin
flags/lifetime to kiprop principal]

ticket: 7979 (new)