Adds check for existing cluster

app/views/projects/clusters/new.html.haml

@@ -5,9 +5,16 @@
   .col-sm-4
     = render 'sidebar'
   .col-sm-8
-    %h4= s_('ClusterIntegration|Choose how to set up cluster integration')
-    %p= s_('ClusterIntegration| Create a new cluster on Google Engine right from GitLab')
-    = link_to s_('ClusterIntegration|Create on GKE'), providers_gcp_new_namespace_project_clusters_path(@project.namespace, @project), class: 'btn append-bottom-20'
-    %p= s_('ClusterIntegration| Enter the details for an existing Kubernetes cluster')
-    = link_to s_('ClusterIntegration|Add an existing cluster'), edit_project_service_path(@project, :kubernetes), class: 'btn append-bottom-20'
+    - if @project.kubernetes_service&.active?
+      %h4.prepend-top-0= s_('ClusterIntegration|Cluster management')
+      %p= s_('ClusterIntegration|A cluster has been set up on this project through the Kubernetes integration page')
+      = link_to s_('ClusterIntegration|Manage Kubernetes integration'), edit_project_service_path(@project, :kubernetes), class: 'btn append-bottom-20'
+
+    - else
+      %h4.prepend-top-0= s_('ClusterIntegration|Choose how to set up cluster integration')
+
+      %p= s_('ClusterIntegration|Create a new cluster on Google Container Engine right from GitLab')
+      = link_to s_('ClusterIntegration|Create on GKE'), providers_gcp_new_namespace_project_clusters_path(@project.namespace, @project), class: 'btn append-bottom-20'
+      %p= s_('ClusterIntegration|Enter the details for an existing Kubernetes cluster')
+      = link_to s_('ClusterIntegration|Add an existing cluster'), edit_project_service_path(@project, :kubernetes), class: 'btn append-bottom-20'