introduce a new environment setting for Active directory client resource uri
remove not used endpoint url
Merge branch 'dev' into mcsubscription
address code review feedback
throw out the exceptions of missing settings at right place
Merge branch 'dev' into mcsubscription
Add help
Merge pull request #2599 from yugangw-msft/mcsubscription

(Resubmit after repository restructuring)Expose a new property from azure subscription for mooncake