[FTR][BugFix] Fix for Failed FTR cis integration (elastic#175396)

## Summary

This PR is to address failed/flaky ftr

https://github.com/orgs/elastic/projects/705/views/8?filterQuery=area%3A%22Cloud+Risk+Mgmt%22+sprint%3A%40current+assignee%3Aanimehart&pane=issue&itemId=43745926
The test fails due to the page is still loading. This PR adds a wait for
the page to fully load first before doing the test steps

x-pack/test/cloud_security_posture_functional/page_objects/add_cis_integration_form_page.ts

@@ -131,6 +131,7 @@ export function AddCisIntegrationFormPageProvider({
       'integrations/cloud_security_posture/add-integration/cspm',
       { shouldUseHashForSubUrl: false }
     );
+    await PageObjects.header.waitUntilLoadingHasFinished();
   };
 
   const navigateToAddIntegrationCnvmPage = async () => {
@@ -139,6 +140,7 @@ export function AddCisIntegrationFormPageProvider({
       'integrations/cloud_security_posture/add-integration/vuln_mgmt',
       { shouldUseHashForSubUrl: false }
     );
+    await PageObjects.header.waitUntilLoadingHasFinished();
   };
 
   const navigateToIntegrationCspList = async () => {
@@ -150,6 +152,7 @@ export function AddCisIntegrationFormPageProvider({
         shouldLoginIfPrompted: false,
       }
     );
+    await PageObjects.header.waitUntilLoadingHasFinished();
   };
 
   const clickPolicyToBeEdited = async (name: string) => {