always works even if the layer is not added to a map. Also removed an
unneeded map.events.unregister from Control.SelectFeature. r=elemoine
(closes#2022)
git-svn-id: http://svn.openlayers.org/trunk/openlayers@9160 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf