Return more data in rpc.call_volume_list

Currently, the volume_list call returns only the volume size. However,
it is useful to also have two other things: the 'inactive' state of the
volume (which might trigger a ‘vgchange -a y’ on the volume group) and
the online state (which shows if the volume is in use or not).

Since this modifies an RPC call, we also bump the protocol version,
although the single user of the call didn't care about the dictionary
values, only about the keys.

Reviewed-by: imsnah