adtrust: define Guests mapping after creating cifs/ principal

All Samba utilities load passdb modules from the configuration file. As
result, 'net groupmap' call would try to initialize ipasam passdb module
and that one would try to connect to LDAP using Kerberos authentication.

We should be running it after cifs/ principal is actually created in
ipa-adtrust-install or otherwise setting up group mapping will fail.

This only affects new installations. For older ones 'net groupmap' would
work just fine because adtrust is already configured and all principals
exist already.

A re-run of 'ipa-server-upgrade' is a workaround too but better to fix
the initial setup.

Related: https://pagure.io/freeipa/issue/7705
Reviewed-By: Rob Crittenden <rcritten@redhat.com>

ipaserver/install/adtrustinstance.py

@@ -837,8 +837,6 @@ class ADTRUSTInstance(service.Service):
                   self.__create_samba_domain_object)
         self.step("creating samba config registry", self.__write_smb_registry)
         self.step("writing samba config file", self.__write_smb_conf)
-        self.step("map BUILTIN\\Guests to nobody group",
-                  self.__map_Guests_to_nobody)
         self.step("adding cifs Kerberos principal",
                   self.request_service_keytab)
         self.step("adding cifs and host Kerberos principals to the adtrust agents group", \
@@ -850,6 +848,8 @@ class ADTRUSTInstance(service.Service):
         self.step("updating Kerberos config", self.__update_krb5_conf)
         self.step("activating CLDAP plugin", self.__add_cldap_module)
         self.step("activating sidgen task", self.__add_sidgen_task)
+        self.step("map BUILTIN\\Guests to nobody group",
+                  self.__map_Guests_to_nobody)
         self.step("configuring smbd to start on boot", self.__enable)
         self.step("adding special DNS service records", \
                   self.__add_dns_service_records)