webadmin: add 'update on next restart' dialog

On update running VM such that part of the changed configuration can be
applied only when the VM will be restarted, new dialog is presented with
a proper message and the user can choose whether cpu changes (if exist)
will be applied immediately or later.

Change-Id: Ic2d7a5fa18bc2df73d5e9d898cd3f23f52fdf0ba
Signed-off-by: Arik Hadas <ahadas@redhat.com>