webadmin: improve the console tab UI

This patch fix the UI brokeness in the console TAB of the VM popup introduced
by the new spice tuning options.

Change-Id: Ifd7820ebcd6732eb3bba4e4a462d10653dbf10d5
Bug-Url: https://bugzilla.redhat.com/1115327
Signed-off-by: Francesco Romani <fromani@redhat.com>