webadmin: Enable vertical scrolling in bond dialog

This is required since the addition of labels, of which many could
exist.

Change-Id: I54ae2350eeb1dc23b222915f99df8f15882c67ae
Bug-Url: https://bugzilla.redhat.com/1063852
Signed-off-by: Lior Vernia <lvernia@redhat.com>