hammer2 - dmsg blockdev work
* Adjust the LNK_CONN and LNK_SPAN messages to provide a cluster label
and a filesystem label instead of just a filesystem label.
* Change the cluster controller to index clusters based on the
peer_type, pfs_clid, and cl_label instead of just the pfs_clid.
HAMMER2 PFS's are primarily identified by pfs_clid and unique nodes
are identified by pfs_fsid. fs_label holds the HAMMER2 super-root
name.
BLOCK devices are primarily identified by cl_label and unique nodes
are identified by pfs_fsid. pfs_clid and fs_label are empty.
* Adjust the cluster controller's matching filters such that, e.g.
BLOCK device clients only have visibility to the BLOCK device server
for the cl_label in question, and do not have visibility to other
BLOCK device clients.
* Flesh out the hammer2 service daemons disk monitoring, have it attach
a pipe to the in-kernel disk via an ioctl().
* Continued work on the skeleton network disk exporter (kern/subr_disk*) and
network disk importer (dev/disk/xdisk/*). xdisk has not been added to the
build yet.
* Move a few more definitions from HAMMER2 to DMSG.