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>

Frezzle/xen-api,cheng--zhang/xen-api,robertbreker/xen-api,simonjbeaumont/xen-api,thomassa/xen-api,agimofcarmen/xen-api,huizh/xen-api,guard163/xen-api,anoobs/xen-api,koushikcgit/xen-api,rafalmiel/xen-api,robertbreker/xen-api,simonjbeaumont/xen-api,jjd27/xen-api,agimofcarmen/xen-api,agimofcarmen/xen-api,thomassa/xen-api,simonjbeaumont/xen-api,koushikcgit/xen-api,guard163/xen-api,cheng--zhang/xen-api,ravippandey/xen-api,robertbreker/xen-api,huizh/xen-api,cheng--zhang/xen-api,salvocambria/xen-api,cheng-z/xen-api,cheng-z/xen-api,thomassa/xen-api,rafalmiel/xen-api,vasilenkomike/xen-api,srowe/xen-api,agimofcarmen/xen-api,Frezzle/xen-api,djs55/xen-api,vasilenkomike/xen-api,djs55/xen-api,cheng--zhang/xen-api,djs55/xen-api,srowe/xen-api,vasilenkomike/xen-api,agimofcarmen/xen-api,guard163/xen-api,ravippandey/xen-api,jjd27/xen-api,djs55/xen-api,srowe/xen-api,srowe/xen-api,vasilenkomike/xen-api,cheng--zhang/xen-api,robertbreker/xen-api,rafalmiel/xen-api,euanh/xen-api,vasilenkomike/xen-api,euanh/xen-api,srowe/xen-api,jjd27/xen-api,huizh/xen-api,jjd27/xen-api,rafalmiel/xen-api,thomassa/xen-api,salvocambria/xen-api,salvocambria/xen-api,koushikcgit/xen-api,jjd27/xen-api,huizh/xen-api,cheng-z/xen-api,huizh/xen-api,guard163/xen-api,koushikcgit/xen-api,thomassa/xen-api,anoobs/xen-api,anoobs/xen-api,ravippandey/xen-api,ravippandey/xen-api,cheng-z/xen-api,euanh/xen-api,salvocambria/xen-api,robertbreker/xen-api,koushikcgit/xen-api,ravippandey/xen-api,salvocambria/xen-api,anoobs/xen-api,djs55/xen-api,simonjbeaumont/xen-api,simonjbeaumont/xen-api,robertbreker/xen-api,Frezzle/xen-api,cheng-z/xen-api,agimofcarmen/xen-api,euanh/xen-api,huizh/xen-api,salvocambria/xen-api,cheng-z/xen-api,vasilenkomike/xen-api,anoobs/xen-api,cheng--zhang/xen-api,cheng--zhang/xen-api,Frezzle/xen-api,ravippandey/xen-api,guard163/xen-api,rafalmiel/xen-api,euanh/xen-api,cheng-z/xen-api,anoobs/xen-api,Frezzle/xen-api,guard163/xen-api,rafalmiel/xen-api,jjd27/xen-api,djs55/xen-api,simonjbeaumont/xen-api,thomassa/xen-api,euanh/xen-api,koushikcgit/xen-api