Find better solution to remove unstable behavior in Delegated_admin Suite

This issue is based on my previous attempt (https://stash.forgerock.org/projects/QA/repos/pyforge/pull-requests/15972/overview) to fix unstable failures for delegated_admin tests which I fixed by adding sleep()
Input from Ladislav: possible fix could be like this: before making REST call execute GET call on certain endpoint using WUKS and check is this endpoint is ready.