userportal,webadmin: USB Support combo permission fixed

Setting Desktop Virtual Machine >> Console tab >> Spice combo >>
USB Support value = Native in the Edit VM dialog causes NPE in GUI
because this option is wrongly enabled just for webadmin.
Enabled now for portal user, too.

Change-Id: I1cefa8cd69057528218373754343c078f3fd6a42
Bug-Url: https://bugzilla.redhat.com/913625
Signed-off-by: Libor Spevak <lspevak@redhat.com>