title: Update subscription when active messages in the subscription
body: <p>I am using latest Azure service bus .Net core apis to manage subscription in a topic.
  I was trying to Update a subscription using UpdateSubscriptionAsync() API to update the defaultMessageTimeToLive and lockDuration.
  However when I update the subscription where a message is being processed, I got "SessionLockLostException: Session lock lost. Accept a new session is force detached"</p>
  
  <p>Is that expected? 
  I did not see any documentation warning against updating a subscription. Are we suppose to check that there are no messages in subscription before updating it?</p>