Establish a way to deal with namespace collision on creation

[andrewjstone]

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Namespace creation is not a cluster wide synchronous process. A namespace is created by an admin user at a given node. This initial namespace configuration is then gossiped across nodes.

This means 2 bad things are possible:

• The node dies before gossiping to the rest of the cluster.
• Users simultaneously create namespaces with the same name on different nodes.

We can prevent both of these by creating a system provided root namespace to allow consistent namespace creation.

[andrewjstone]

Since we are going to likely use a root namespace to allow consistent deletion of namespaces we may as well add this to the diskless 1.0 milestone as well. It's not hard to implement.