Block Storage API mv 3.66 enables snapshots of in-use volumes
without requiring a 'force' flag. For backward compatibility,
the API silently accepts force=true, even though the 'force' flag
is considered invalid for that call. That behavior is replicated
in the client, where --force with a true value is silently accepted.
The --force option is not advertised in the shell and an option
value that doesn't evaluate to true raises an UnsupportedAttribute
error. Similar behavior from the v3 Snapshot class, except it
raises a ValueError under similar circumstances.
Change-Id: I7408d0e3a5ed7f4cbcaf65cf3434ad60aaed511d
c3c15f6cb2