Update create_execution_environment to pass the chart_model

The function create_execution_environment has been updated
to allow the deployment from a file or from a reference
(repo/name:version).

This will call to the N2VC Helm connector to install the execution
environment in the local environment.

Change-Id: I03c8e95bf0f6a55d3f62bc7a55dabe3a9b348cde
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>