Bug 1981 fixed

Added the `yaml_format` argument to the `status_kdu` abstract method of
the class `K8sConnector`, and changed the corresponding Helm connectors
methods accordingly, while maintaining backward compatibility

Change-Id: Ic78c951825b7654ccf8246c4fe1fc4d488221bfc
Signed-off-by: Pedro Escaleira <escaleira@av.it.pt>