Switch to using the Disk management from the Barclamp library

This, among other things allows to use cinder and swift
storage on the same node, and also opens the way for future code
cleanup.
Remove disk_enum_expr and disk_test_expr

Both attributes are now entirely unused.
Detach devices that do not have a matching UUID anymore

Otherwise applying the barclamp fails after replacing harddrives
(or when reapplying a newly created proposal).
Ignore mount errors on boot

If an (old) Swift device cannot be mounted anymore, ignore
that and let chef-client clean it up.