Remove python3.5 jobs for Train

The TC has decided that python 3.5 tests are not required for Train
forward[1]. This patch removes the python 3.5 jobs from octavia-lib.

[1] http://lists.openstack.org/pipermail/openstack-discuss/2019-April/ \
    005097.html

Change-Id: Ice875dde4eeb82962f3c635cb312f157d9a8331a

setup.cfg

@@ -19,7 +19,6 @@ classifier =
     Programming Language :: Python :: 2
     Programming Language :: Python :: 2.7
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.5
     Programming Language :: Python :: 3.6
 
 [files]

tox.ini

@@ -1,6 +1,6 @@
 [tox]
-minversion = 2.0
-envlist = docs,py35,py27,pep8
+minversion = 2.5.0
+envlist = docs,py36,py27,pep8
 skipsdist = True
 
 [testenv]

zuul.d/projects.yaml

@@ -4,7 +4,6 @@
       - openstack-cover-jobs
       - openstack-lower-constraints-jobs
       - openstack-python-jobs
-      - openstack-python35-jobs
       - openstack-python36-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3