Allow the usage of external address (#938)

Co-authored-by: Devin Buhl <onedr0p@users.noreply.github.com>

bootstrap/vars/config.sample.yaml

@@ -64,10 +64,12 @@ bootstrap_nodes:
     #   address:  # ip address of the master node
     #   username: # ssh username of the master node
     #   password: # password of ssh username for the master node
+    #   # external_address: # Only use when SSH is not reachable on the IP specified in 'address' field
     # ...
   worker: # set to [] or omit if no workers are needed
     # - name:     # name of the worker node (must match [a-z0-9-]+)
     #   address:  # ip address of the worker node
     #   username: # ssh username of the worker node
     #   password: # password of ssh username for the worker node
+    #   # external_address: # Only use when SSH is not reachable on the IP specified in 'address' field
     # ...