set namespace for kubeclient during uninstall

[thorbenbelow]

Fixes #1033 #1558

This should probably be adjusted to still call ensureHelmConfig or use c.Config().Flags() instead of a new helm cli object.

[derailed]

@thorbenbelow Brilliant!! Thank you for your research on this!!

I've taken a pass and it looks like the issue is due to the helm api not taking into account the passed in ns and thus applies the deletions in the context ns.

cli.New call hydrates a new connection from flags and thus uninstall deletes the resources in the chart ns. (Helm deletion manifests don't specify a namespace and thus default to the context namespace.
Does this make sense?

I think we can fix this by doing those 3 things:

1. Turn off persistent config in k9s. See client/config.go UsePersistentConfig
2. Update ensureHelmConfig to take in configFlags vs a connection object
3. Update the Helm uninstall to now read something like:

	flags := h.Client().Config().Flags()
	flags.Namespace = &ns
	cfg, err := ensureHelmConfig(flags, ns)
	...
	
// ensureHelmConfig return a new configuration.
func ensureHelmConfig(flags *genericclioptions.ConfigFlags, ns string) (*action.Configuration, error) {
	cfg := new(action.Configuration)
	err := cfg.Init(flags, ns, os.Getenv("HELM_DRIVER"), helmLogger)

	return cfg, err
}