Improved Primitive support and better testing

This changeset addresses several issues.

- Improve primitive support so the status and output of an executed
primitive can be retrieved
- Merge latest upstream libjuju (required for new primive features)
- New testing framework
    This is the start of a new testing framework with the ability to
create and configure LXD containers with SSH, to use while testing proxy
charms.
- Add support for using ssh keys with proxy charms
    See Feature 1429. This uses the per-proxy charm/unit ssh keypair

Signed-off-by: Adam Israel <adam.israel@canonical.com>
diff --git a/modules/libjuju/examples/credential.py b/modules/libjuju/examples/credential.py
new file mode 100644
index 0000000..e653536
--- /dev/null
+++ b/modules/libjuju/examples/credential.py
@@ -0,0 +1,47 @@
+import sys
+from juju import loop
+from juju.controller import Controller
+
+
+async def main(cloud_name, credential_name):
+    controller = Controller()
+    model = None
+    print('Connecting to controller')
+    # connect to current controller with current user, per Juju CLI
+    await controller.connect()
+    try:
+        print('Adding model')
+        model = await controller.add_model(
+            'test',
+            cloud_name=cloud_name,
+            credential_name=credential_name)
+
+        # verify credential
+        print("Verify model's credential: {}".format(
+            model.info.cloud_credential_tag))
+
+        # verify we can deploy
+        print('Deploying ubuntu')
+        app = await model.deploy('ubuntu-10')
+
+        print('Waiting for active')
+        await model.block_until(
+            lambda: app.units and all(unit.workload_status == 'active'
+                                      for unit in app.units))
+
+        print('Removing ubuntu')
+        await app.remove()
+    finally:
+        print('Cleaning up')
+        if model:
+            print('Removing model')
+            model_uuid = model.info.uuid
+            await model.disconnect()
+            await controller.destroy_model(model_uuid)
+        print('Disconnecting')
+        await controller.disconnect()
+
+
+if __name__ == '__main__':
+    assert len(sys.argv) > 2, 'Please provide a cloud and credential name'
+    loop.run(main(sys.argv[1], sys.argv[2]))