Add discovery for subinterface VLAN-id (Cisco)

Hi!

It would be very useful for us to see which vlan-id is configured on the sub-interface for our cisco-routers.

For example, the following interface is configured:

interface Bundle-Ether99.1234
  encapsulation dot1q 2345
!

There is OID cviVlanInterfaceIndexTable (.1.3.6.1.4.1.9.9.128.1.1.1.1.3)

That OID reveals subinterface - parent interface ** relationship in form:

.1.3.6.1.4.1.9.9.128.1.1.1.1.3.VlanId.parentIfId = subIfId

We are grateful for your help.