Fix for "show run-conf" and "show-vlan"

* reviewed the "get_vdb" function and changed the vlan bitmap
as it was originally planned:
	0 for allowed vlans
	1 for forbidden vlans
* changed only the "linux" back-end and the CLI;
* the LiSA module returns garbage as VLAN bitmap; needs fixes too

Signed-off-by: Claudiu Ghioc <claudiu.ghioc@gmail.com>

Author: Claudiu Ghioc <claudiu.ghioc@gmail.com>
	Martinas Mihaela <martinas.mihaela21.gmail.com>