Fix CI (#188)

* Limit cryptography to < 3.4 for Python < 3.6.

* Make sure cryptography 3.3+ is installed on Darwin.

* Work around old pip versions.

tests/integration/targets/setup_openssl/tasks/main.yml

@@ -89,7 +89,7 @@
   - name: Install cryptography (Darwin)
     become: true
     pip:
-      name: cryptography
+      name: cryptography>=3.3
       extra_args: "-c {{ remote_constraints }}"
     when: ansible_os_family == 'Darwin'