Fix failing unit tests
Fix failing unit tests

Purpose of this commit is to overwrite Django settings of Horizon.
Horizon team decided to set debug flag to True, which causes problem in our tests.

Error occurs after this Horizon commit:
https://github.com/openstack/horizon/commit/b0e9c3135ce129ee01d7c76bc7f34513a35060b7

Change-Id: I4d677bb4522e315ab2e4386193deb52a82d7645f
Story: 2005336
Task: 30274

openstack/monasca-ui,openstack/monasca-ui,openstack/monasca-ui,openstack/monasca-ui,stackforge/monasca-ui,stackforge/monasca-ui,stackforge/monasca-ui,stackforge/monasca-ui