OVS UT: Fix some confusions between local vlan id and segmentation id

OVS UT: Fix some confusions between local vlan id and segmentation id

Also, use different values for them to expose mistakes.

Details:

There are two kinds of vlan ids involved here:
* local vlan id, which is managed by each agents in a node-local manner.
* segmentation id, which is managed by the corresponding ML2 type driver.
These tests use the distinct variables for them.
(LV_ID and LS_ID respectively)
However, these variables are misused in some places, relying on the fact
that their values are same.  (42)

Change-Id: Ib2ba74be74c2c361d25821acab2083a17b1b0173