fix for qrewrite failing with dataset wildcards (in testbed, needs patching)

* qrewrite was creating a DASQuery({spec: dataset.name='<PK>', ...})
    which was not passing wildcard validation (since wildcard check do not need dbsmanager to be passed).
* the simple fix is to pass a valid dataset name instead (e.g. /a/b/c)

P.S. the patch is based directly on 2.3.0 tag.