[Discovery] do not use versions to optimize cluster state copying for a first update from a new master

We have an optimization which compares routing/meta data version of cluster states and tries to reuse the current object if the versions are equal. This can cause rare failures during recovery from a minimum_master_node breach when using the "new light rejoin" mechanism and simulated network disconnects. This happens where the current master updates it's state, doesn't manage to broadcast it to other nodes due to the disconnect and then steps down. The new master will start with a previous version and continue to update it. When the old master rejoins, the versions of it's state can equal but the content is different.

**NOTE:** this a PR for the feature/improve_zen branch
See: https://github.com/elasticsearch/elasticsearch/pull/6466/files#diff-7e704e723d968699a880ef44818125efR484