Add option to allow multiple access points to cache

If you have hpc-cache (or a ceph file cache) sitting in front of some remote storage there are often multiple load balanced instances.

Add an option to the platform to allow multiple pvcs for the different instances to be mounted, and then decide which instance to target based on the hash of the filename.  It will need to add an extra leading component to the path to select between the different instances.  (This is in addition to the striping directory).

Questions:

• What about failover?  Can we swap to a different instance?  I suspect tricky
• Do we support for non-aliases, or is it only aliases?