webadmin: Improve add/edit network dialog alignment

Alignment was off in Chrome, this is an attempt to fix this.

Change-Id: I629500f6617f8b146411b8e18eec8e0c9b16d240
Bug-Url: https://bugzilla.redhat.com/1057305
Signed-off-by: Lior Vernia <lvernia@redhat.com>