Fix feature spec Clusters Applications (#17052)

We need to actually wait for the "Install" button to be enabled before clicking it otherwise we have a race condition where it sometimes works. Also change the `expect(page.find(...))` to `expect(page).to have_css` as this is prefered to avoid race conditions

spec/features/projects/clusters/applications_spec.rb

@@ -78,6 +78,7 @@ feature 'Clusters Applications', :js do
             create(:clusters_applications_helm, :installed, cluster: cluster)
 
             page.within('.js-cluster-application-row-ingress') do
+              expect(page).to have_css('.js-cluster-application-install-button:not([disabled])')
               page.find(:css, '.js-cluster-application-install-button').click
             end
           end
@@ -85,20 +86,20 @@ feature 'Clusters Applications', :js do
           it 'he sees status transition' do
             page.within('.js-cluster-application-row-ingress') do
               # FE sends request and gets the response, then the buttons is "Install"
-              expect(page.find(:css, '.js-cluster-application-install-button')['disabled']).to eq('true')
+              expect(page).to have_css('.js-cluster-application-install-button[disabled]')
               expect(page).to have_css('.js-cluster-application-install-button', exact_text: 'Install')
 
               Clusters::Cluster.last.application_ingress.make_installing!
 
               # FE starts polling and update the buttons to "Installing"
-              expect(page.find(:css, '.js-cluster-application-install-button')['disabled']).to eq('true')
               expect(page).to have_css('.js-cluster-application-install-button', exact_text: 'Installing')
+              expect(page).to have_css('.js-cluster-application-install-button[disabled]')
 
               # The application becomes installed but we keep waiting for external IP address
               Clusters::Cluster.last.application_ingress.make_installed!
 
-              expect(page.find(:css, '.js-cluster-application-install-button')['disabled']).to eq('true')
               expect(page).to have_css('.js-cluster-application-install-button', exact_text: 'Installed')
+              expect(page).to have_css('.js-cluster-application-install-button[disabled]')
               expect(page).to have_selector('.js-no-ip-message')
               expect(page.find('.js-ip-address').value).to eq('?')