webadmin: Add room for long vNIC names

Increased the width of the label field, and redesigned the widgets
around it to conform to the new width.

Change-Id: I6f7d73632440d88e76c544a1aee754f47bdf8f21
Bug-Url: https://bugzilla.redhat.com/1029973
Signed-off-by: Lior Vernia <lvernia@redhat.com>