Fix minor issue in LCMHelmConn

scaling_in argument has been added to the delete_execution_environment
for the juju connector. This patch adds kwargs to the helm connector.
The scaling_in is not currently used by helm.

Change-Id: I4723d6f194cdd64a4b3bbef348457fb6c2a1e47c
Signed-off-by: David Garcia <david.garcia@canonical.com>