Login/Logout redirects with Django variables

The login/logout url patterns now use
the Django LOGIN_URL and LOGOUT_URL

The default redirect url after a successful login
now uses as default the Django LOGIN_REDIRECT_URL
with possible override using HORIZON_CONFIG.user_home
in settings file. There are 3 cases:

* no user_home in settings.HORIZON_CONFIG - uses
Django LOGIN_REDIRECT_URL
* user_home = None in settings.HORIZON_CONFIG -
will default to the primary dashboard(the current
fall-back behavior)
* user_home = 'something' - it will be used to
determine the actual redirect url

Fixes bug 980434

Patch Set 2:
Restored the previous behavior - splash page('/')
redirects to /nova or /syspanel, depending on the user,
while /home/ will redirect to the 'user_home' setting
(or LOGIN_REDIRECT_URL if user_home is not set).
The same logic will be applied after user logs in.

Change-Id: I28e25566199393382639da9ca2022d1850f25a94

horizon/base.py

@@ -52,7 +52,8 @@ HORIZON_CONFIG = {
     'dashboards': None,
     # Name of a default dashboard; defaults to first alphabetically if None
     'default_dashboard': None,
-    'user_home': None,
+    # Default redirect url for users' home
+    'user_home': settings.LOGIN_REDIRECT_URL,
     'exceptions': {'unauthorized': [],
                    'not_found': [],
                    'recoverable': []}
@@ -700,9 +701,11 @@ class Site(Registry, HorizonComponent):
             {"user_home": "/home",}  # A URL
             {"user_home": "my_module.get_user_home",}  # Path to a function
             {"user_home": lambda user: "/" + user.name,}  # A function
+            {"user_home": None,}  # Will always return the default dashboard
 
         This can be useful if the default dashboard may not be accessible
-        to all users.
+        to all users. When user_home is missing from HORIZON_CONFIG,
+        it will default to the settings.LOGIN_REDIRECT_URL value.
         """
         user_home = self._conf['user_home']
         if user_home: