Ensure `Namespace`'s is namespaced in `Gitlab::Kubernetes::Helm#initialize`...

Ensure `Namespace`'s is namespaced in `Gitlab::Kubernetes::Helm#initialize` and fix a transient failing spec due to that
Signed-off-by: Rémy Coutable <remy@rymai.me>

lib/gitlab/kubernetes/helm.rb

@@ -18,7 +18,7 @@ module Gitlab
 
       def initialize(kubeclient)
         @kubeclient = kubeclient
-        @namespace = Namespace.new(NAMESPACE, kubeclient)
+        @namespace = Gitlab::Kubernetes::Namespace.new(NAMESPACE, kubeclient)
       end
 
       def install(command)

spec/services/clusters/applications/schedule_installation_service_spec.rb

@@ -22,6 +22,8 @@ describe Clusters::Applications::ScheduleInstallationService do
     let(:service) { described_class.new(project, nil, cluster: cluster, application_class: application_class) }
 
     it 'creates a new application' do
+      allow(ClusterInstallAppWorker).to receive(:perform_async)
+
       expect { service.execute }.to change { application_class.count }.by(1)
     end