Don't perform upgrade if version hasn't changed

Currently, when running Mayan in k8s and its pod(s) get re-scheduled for whatever reason, entrypoint.sh performs an upgrade even when the new pod is running the same version as its previous incarnation. This results in slow recovery times (up to 5 minutes). The upgrade process also requires an outgoing Internet connection to an npm repo which is not ideal for us when we pre-set up Mayan EDMS at the office and then move it off-site where there is no Internet connection.

This change skips the upgrade process if entrypoint.sh finds that the Mayan version it's trying to bring up is the same version as the previous incarnation.