Add a means of deregistering interdomain RRD plugins
Add a means of deregistering interdomain RRD plugins

A plugin will be deregistered if it writes "true" to
/local/domain/<domid>/rrd/<plugin-name>/shutdown

Signed-off-by: John Else <37b74501daa612e48fea94f9846ed4ddeb6a8f07@citrix.com>

djs55/xenopsd,euanh/xenopsd,koushikcgit/xenopsd,thomassa/xenopsd,djs55/xenopsd-previous,johnelse/xenopsd,djs55/xenopsd-previous,johnelse/xenopsd,cheng--zhang/xenopsd,simonjbeaumont/xenopsd,thomassa/xenopsd,djs55/xenopsd,johnelse/xenopsd,djs55/xenopsd-previous,euanh/xenopsd,cheng--zhang/xenopsd,simonjbeaumont/xenopsd,simonjbeaumont/xenopsd,koushikcgit/xenopsd,cheng--zhang/xenopsd,euanh/xenopsd,thomassa/xenopsd,koushikcgit/xenopsd,djs55/xenopsd