Fix django LOGOUT_URL parameter for Ubuntu and CentOS.

This commit should be reverted as soon as bug
https://bugs.launchpad.net/ubuntu/+source/horizon/+bug/1243187
is fixed.
Change-Id: I7fb20586857221e8ea7d9ea08e6cdafdf2aab56b
Merge "Fix django LOGOUT_URL parameter for Ubuntu and CentOS."