Make API Proxy optional and avoid replacing existing SSH Keys in the provisioner

- Fixes bug 1154
- Fixes bug 1083
Change-Id: I0ee5e092f5ff205089c2b80ece9f4262572d58d2
Signed-off-by: David Garcia <david.garcia@canonical.com>
diff --git a/n2vc/libjuju.py b/n2vc/libjuju.py
index 22ba182..cb24a3e 100644
--- a/n2vc/libjuju.py
+++ b/n2vc/libjuju.py
@@ -408,7 +408,7 @@
                     connection=connection,
                     nonce=params.nonce,
                     machine_id=machine_id,
-                    api=self.api_proxy,
+                    proxy=self.api_proxy,
                 )
             )