Add use_ssh_client flag (#114)

* Add use_ssh_client option.

* Unrelated cleanup (unneeded imports).

* Add SSH connection tests.

tests/integration/targets/setup_paramiko/meta/main.yml

@@ -0,0 +1,4 @@
+---
+dependencies:
+  - setup_remote_constraints
+  - setup_openssl  # so cryptography is installed

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

@@ -0,0 +1,6 @@
+---
+- name: Install paramiko
+  pip:
+    name: "paramiko{% if cryptography_version.stdout is version('2.5.0', '<') %}<2.5.0{% endif %}"
+    extra_args: "-c {{ remote_constraints }}"
+  become: true