Add test for HTTP PrimaryStorageDownloadCommand.
Temporarily disable other tests while working on HTTP download feature.
Clean up NFS client work around.  NFS URLs resolve to local path specified in config via local.secondary.storage.path
Revise implementation of PrimaryStorageDownloadCommand.  Now expects the URL field of the command to be a URI for the template.  I.e. it should be the location of the file, and not merely the folder containing the file.
Clean up comments.
Update validation to throw if the physical volume name and file name portion of path do not match.
Also, throw if the extension is invalid.
Shift details of the local path for secondary storage NFS to the StorageAdaptor.
Remove methods that are unused in light of changes to DownloadPrimaryStorageCommand
Expose ability to copy a disk identitifed by URI into a primary storage.
Remove unused methods from StoreageAdaptor interface.
iRemove unused methods.
Update StoragePool capacity measures when a refresh occurs.
Introduce ability to create a disk from a URI.
Use a configured local path to resolve NFS paths in lieu of a client to mount the NFS storage.
HTTP is the other supported URI schema.
However, the HTTP download is yet to be tested, and may need to be fixed.
Expose a refresh operation for StoragePools.  Underlying code should update StoragePool capacity measures when a refresh occurs.
Fix HTTP schema support for DownloadPrimaryStorageDownload command.
Fix StoragePool refresh to allow it to record changes in capacity.
Activate all supported tests.