adtrustinstance: Wait for sidgen task completion

As part of hardening of adtrust installer, we should wait until
the sidgen task is completed before continuing, as it can take
considerable amount of time for a larger deployment.

https://fedorahosted.org/freeipa/ticket/5134

Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>

ipaserver/install/adtrustinstance.py

@@ -34,6 +34,7 @@ from ipaserver.install import service
 from ipaserver.install import installutils
 from ipaserver.install.bindinstance import get_rr, add_rr, del_rr, \
                                            dns_zone_exists
+from ipaserver.install.replication import wait_for_task
 from ipalib import errors, api
 from ipalib.util import normalize_zone
 from ipapython.dn import DN
@@ -469,13 +470,24 @@ class ADTRUSTInstance(service.Service):
 
     def __add_sids(self):
         """
-        Add SIDs for existing users and groups
+        Add SIDs for existing users and groups. Make sure the task is finished
+        before continuing.
         """
 
         try:
+            # Start the sidgen task
             self._ldap_mod("ipa-sidgen-task-run.ldif", self.sub_dict)
-        except:
-            pass
+
+            # Notify the user about the possible delay
+            self.print_msg("This step may take considerable amount of time, please wait..")
+
+            # Wait for the task to complete
+            task_dn = DN('cn=sidgen,cn=ipa-sidgen-task,cn=tasks,cn=config')
+            wait_for_task(self.admin_conn, task_dn)
+
+        except Exception as e:
+            root_logger.warning("Exception occured during SID generation: {0}"
+                                .format(str(e)))
 
     def __add_s4u2proxy_target(self):
         """