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 and
lower-constraints.txt are updated accordingly. for more info. please
refer [1].
Depends-On: https://review.opendev.org/#/c/700733/
[1] https://etherpad.openstack.org/p/Enable_Django22_support_in_Horizon_Plugin

Change-Id: If78d9ce4206dae403f0cc03eb3c8601ba3bab752

lower-constraints.txt

@@ -13,7 +13,7 @@ cryptography==2.1
 debtcollector==1.2.0
 decorator==3.4.0
 deprecation==1.0
-Django==1.11
+Django==2.2
 django-appconf==1.0.2
 django-babel==0.6.2
 django-compressor==2.0
@@ -30,7 +30,7 @@ flake8-import-order==0.13
 futurist==1.2.0
 greenlet==0.4.10
 hacking==0.12.0
-horizon==14.0.0
+horizon==17.1.0
 idna==2.6
 imagesize==0.7.1
 iso8601==0.1.11
@@ -87,10 +87,10 @@ pyOpenSSL==17.1.0
 pyparsing==2.1.0
 pyperclip==1.5.27
 pyScss==1.3.4
-python-cinderclient==3.3.0
+python-cinderclient==5.0.0
 python-dateutil==2.5.3
 python-glanceclient==2.8.0
-python-keystoneclient==3.15.0
+python-keystoneclient==3.22.0
 python-mimeparse==1.6.0
 python-neutronclient==6.7.0
 python-novaclient==9.1.0

requirements.txt

@@ -3,5 +3,5 @@
 # process, which may cause wedges in the gate later.
 
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
-horizon>=14.0.0 # Apache-2.0
+horizon>=17.1.0 # Apache-2.0
 python-neutronclient>=6.7.0 # Apache-2.0

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
@@ -18,8 +18,6 @@ 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
   python manage.py test {posargs} --settings=neutron_vpnaas_dashboard.test.settings
 
 [testenv:pep8]