webadmin: css: widen contentWidget class.

Prevent overflows in widgets with longer text. e.g FR in addHost->
PowerManagement dialog.

Change-Id: Ie39b55bcdbf110113d9b8e607afafef96bb0783e
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1123324
Signed-off-by: Mooli Tayer <mtayer@redhat.com>