Optionally wait for 389-ds postop plugins to complete

Add a new command that lets you wait for an attribute to appear in
a value. Using this you can do things like wait for a managed entry
to be created, adding a new objectclass to the parent entry.

This is controlled by a new booleon option, wait_for_attr, defaulting
to False.

https://fedorahosted.org/freeipa/ticket/1144

tests/test_xmlrpc/objectclasses.py

@@ -21,7 +21,7 @@
 Defines the expected objectclass for various entries.
 """
 
-user = [
+user_base = [
     u'top',
     u'person',
     u'organizationalperson',
@@ -33,6 +33,8 @@ user = [
     u'ipaobject',
 ]
 
+user = user_base + [u'mepOriginEntry']
+
 group = [
     u'top',
     u'groupofnames',