Use namespace for release unicity with helm3 (#1213) (#1235)

This is for #1213 so that the releases are considered scoped to their namespace and not to tiller namespace.

Fixes #1213

pkg/app/mocks_test.go

@@ -5,6 +5,15 @@ import "github.com/roboll/helmfile/pkg/helmexec"
 type noCallHelmExec struct {
 }
 
+type versionOnlyHelmExec struct {
+	*noCallHelmExec
+	isHelm3 bool
+}
+
+func (helm *versionOnlyHelmExec) IsHelm3() bool {
+	return helm.isHelm3
+}
+
 func (helm *noCallHelmExec) doPanic() {
 	panic("unexpected call to helm")
 }