webadmin: Resized edit DC network dialog

It was too small, changed the size to be exactly like the normal edit
network dialog.

Change-Id: I5777d41bb6b353128eaf35ccbc2f8a5f98388f1d
Bug-Url: https://bugzilla.redhat.com/996612
Signed-off-by: Lior Vernia <lvernia@redhat.com>