Update scripts/block for blkback's new pause/resume ops.
Update scripts/block for blkback's new pause/resume ops.

The kernel can emit uevents when quiescing a VBD's I/O queue. It won't
write pause-done, but signal state changes through a new key:
queue-state. The basic idea is to let storage-level code hook into
pause/resume transitions where desirable. This script implements a
default handler.

The original device.ml protocol remains as is, but the implementation
differs:

 * ACTION=add:    request queue-state change notifications.
 * ACTION=change: translate queue-state to pause-done.

Also adds a bit more verbosity to the daemon.log.

Signed-off-by: Daniel Stodden <05f14ed2a2851619d24030f51bb8d7a9bac70353@citrix.com>

sharady/xcp-networkd,simonjbeaumont/xcp-rrdd,koushikcgit/xcp-networkd,johnelse/xcp-rrdd,robhoes/squeezed,koushikcgit/xcp-networkd,djs55/xcp-rrdd,koushikcgit/xcp-rrdd,simonjbeaumont/xcp-rrdd,djs55/xcp-networkd,koushikcgit/xcp-rrdd,johnelse/xcp-rrdd,djs55/squeezed,djs55/xcp-networkd,koushikcgit/xcp-rrdd,sharady/xcp-networkd,djs55/xcp-rrdd