tools: xencommons NetBSD init script: Multiple bugfixes and improvements

tools: xencommons NetBSD init script: Multiple bugfixes and improvements

Added a cleanup of the xenstore database, to purge old entries,
prevented the restart of xenstore and set Domain-0 name.  Also
replaced the sleep 5 (wait for xenstore to come up) with the method
used in the linux init script.

Signed-off-by: Roger Pau Monne <roger.pau@entel.upc.edu>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Christoph Egger <Christoph.Egger@amd.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>