Make registry hostrealm module highest precedence

Make registry hostrealm module highest precedence

Testing reveals that there are a number of machines in the wild
which retain old krb5.ini files across domain configuration changes,
and it is difficult to determine which machines are potentially
affected by incorrect stale configuration data.

To enable domain administrators to easily ensure that the correct
default realm is set, allow the registry hostrealm module to take
precedence over the profile.

Note that the registry hostrealm module can still be disabled
in the hostrealm interface configuration statment in the
[plugins] section of the profile.

ticket: 8209 (new)
subject: stale krb5.ini files still cause default realm WIN.MIT.EDU
tags: pullup
target_version: 1.13.3