Bug 1962 fixed: removed the variable cluster_uuid from init_env method

This was applied to the class K8sHelmBaseConnector, and then returned
the variable cluster_id instead of cluster_uuid;

Also, refactored the overall Helm related code, in order to use the correct cluster uuid (and fixed the corresponding tests);

Also made a small fix in the function _uninstall_sw, to remove the service accounts when using different namespaces

Change-Id: Ibfdc82f325abf5fd27a225e73f949483a4e68fe2
Signed-off-by: Pedro Escaleira <escaleira@av.it.pt>