Fix addattr internal error

When ADD command is being executed and a single-value object attribute
is being set with both option and addattr IPA ends up in an internal
error.

Make better value sanitizing job in this case and let IPA throw
a user-friendly error. Unit test exercising this situation is added.

https://fedorahosted.org/freeipa/ticket/2429

ipalib/plugins/baseldap.py

@@ -882,7 +882,17 @@ last, after all sets and adds."""),
             entry_attrs[attr] = val
 
         for attr in direct_add:
-            entry_attrs.setdefault(attr, []).extend(adddict[attr])
+            try:
+                val = entry_attrs[attr]
+            except KeyError:
+                val = []
+            else:
+                if not isinstance(val, (list, tuple)):
+                    val = [val]
+                elif isinstance(val, tuple):
+                    val = list(val)
+            val.extend(adddict[attr])
+            entry_attrs[attr] = val
 
         for attr in direct_del:
             for delval in deldict[attr]:

tests/test_xmlrpc/test_attr.py

@@ -36,6 +36,16 @@ class test_attr(Declarative):
 
     tests = [
 
+        dict(
+            desc='Try to add user %r with single-value attribute set via '
+                 'option and --addattr' % user1,
+            command=(
+                'user_add', [user1], dict(givenname=u'Test', sn=u'User1',
+                    addattr=u'sn=User2')
+            ),
+            expected=errors.OnlyOneValueAllowed(attr='sn'),
+        ),
+
         dict(
             desc='Create %r' % user1,
             command=(