webadmin: Pass validation when QoS widget is hidden

In lower cluster compatibility versions the QoS widget is hidden when
editing a network attached to a host, in this case it should be
considered valid for the dialog to be approved.

Change-Id: I8d9833d3e66aacb60539b4f0f9e550d194f0ef0a
Bug-Url: https://bugzilla.redhat.com/1054314
Signed-off-by: Lior Vernia <lvernia@redhat.com>