tox tests: pin test requirement versions

Tests started failing once ansible 2.3 was released. It seems wise to
pin the dependencies to particular versions until we make a conscious
decision to change them (and have tested with them).

requirements.txt

@@ -1,6 +1,6 @@
-ansible>=2.2
-click
-pyOpenSSL
+ansible==2.2.2.0
+click==6.7
+pyOpenSSL==16.2.0
 # We need to disable ruamel.yaml for now because of test failures
 #ruamel.yaml
-six
+six==1.10.0