Vlan could not be deleted once ip-address is configured on it.

Vlan could not be deleted once ip-address is configured on it.

```
Soft-Firewall>$ config-node-R1-interface-vlan-10> 
Soft-Firewall>$ config-node-R1-interface-vlan-10> ip-address 10.1.1.1 24
Soft-Firewall>$ config-node-R1> no interface vlan 10 ip-address 10.1.1.1 24
Soft-Firewall>$ config-node-R1> no interface vlan 10
Error : Vlan is in use

Soft-Firewall>$ config-node-R1> 
```