Drop Django 1.11 support

Django 1.11 ends its extended support in April 2020 (which is before
Ussuri release), so horizon drops Django 1.11 support in Ussuri.

tox envs for non-primary Django versions are no longer needed in tox.ini
as testing environments for non-primary Django versions are setup in
the zuul jobs now.

horizon>=17.1.0 is required to use Django 2.2.
requirements.txt is updated accordingly.
For more info. please refer [1], [2].

[1] https://review.opendev.org/#/c/700733/
[2] https://etherpad.openstack.org/p/Enable_Django22_support_in_Horizon_Plugin

Change-Id: Ifc49a69d4b34b32d64a95cca488c3a1ab7eb2ef6

requirements.txt

@@ -8,9 +8,10 @@
 #
 # PBR should always appear first
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
-Django<2,>=1.11;python_version<'3.0' # BSD
-Django<3.0,>=1.11;python_version>='3.0'  # BSD
+Django>=2.2,<3.0 # BSD
 django-compressor>=2.0 # MIT
 django-pyscss>=2.0.2 # BSD License (2 clause)
 python-karborclient>=0.6.0 # Apache-2.0
 icalendar>=4.0.2 # BSD
+
+horizon>=17.1.0 # Apache-2.0

test-requirements.txt

@@ -19,5 +19,3 @@ sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2 # BSD
 testtools>=2.2.0 # MIT
 # This also needs xvfb library installed on your OS
 xvfbwrapper>=0.1.3 #license: MIT
-# Include horizon as test requirement
-http://tarballs.openstack.org/horizon/horizon-master.tar.gz#egg=horizon

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py37,py3-{dj111,dj22},pep8
+envlist = py37,pep8
 minversion = 3.1.1
 skipsdist = True
 ignore_basepython_conflict = True
@@ -15,8 +15,6 @@ setenv = VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands =
-   dj111: pip install django>=1.11,<2
-   dj22: pip install django>=2.2,<2.3
    {toxinidir}/manage.py test karbor_dashboard --settings=karbor_dashboard.test.settings
 
 [testenv:pep8]