Move the 'run' function to the Common module.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Support NFS mounts

We support both
  device-config:location=[<path>|<server>:<path>]
(as used by the old ISO SR)

and
  device-config:path=[<path>|<server>:<path>]

Signed-off-by: David Scott <dave.scott@eu.citrix.com>