Upgrade feature improvement - Nuget update

Minimizes downtime associated with upgrading. In particular, when an upgrading secondary is created and catches up to the primary, the primary dies and the old secondaries are suspended. If the upgrade is successful, all secondaries die and new ones using the new version of the code may be deployed. If the upgrade is unsuccessful, the suspended secondaries wake up, and one is promoted to become a primary, and the old version of the code continues to run. This change eliminates the recovery time from potential downtime while upgrading.