Bump pyflakes and pin ansible-lint

We need a python 3.9 compatible version of pyflakes and we need to
pin ansible-lint to an ansible 2.7 compatible version.

Related PyCQA/pyflakes #367

Change-Id: Iedc76eb82d831cad8dfc569477eece827aca750c

ansible-requirements.txt

@@ -3,4 +3,4 @@
 # lint checks and want to document these as ansible specific things that may
 # be required for this repository.
 ansible==2.7.6
-ansible-lint
+ansible-lint<=4.0.0

requirements.txt

@@ -1,2 +1 @@
 pbr>=1.6
-ansible

test-requirements.txt

@@ -1 +1,2 @@
 hacking!=0.13.0,<0.14,>=0.12.0 # Apache-2.0
+pyflakes>=2.2.0