Fix an error which cause on Feb 29 in user setting

In Feb 29(leap year), when users update user settings, error will occur.
Settings expiration is a year later and this calculation is incorrect.
This patch will fix it.

Change-Id: Id2bc6741ad3366969fbb73dc64c23430ce66f2aa
Closes-Bug: #1551099
(cherry picked from commit 79c531a1c4)

openstack_dashboard/dashboards/settings/user/forms.py

@@ -13,6 +13,7 @@
 #    under the License.
 
 from datetime import datetime  # noqa
+from datetime import timedelta  # noqa
 import string
 
 import babel
@@ -30,8 +31,7 @@ from horizon import messages
 
 def _one_year():
     now = datetime.utcnow()
-    return datetime(now.year + 1, now.month, now.day, now.hour,
-                    now.minute, now.second, now.microsecond, now.tzinfo)
+    return now + timedelta(days=365)
 
 
 class UserSettingsForm(forms.SelfHandlingForm):