For symmetrical links, we need to maintain links both ways in our cache of ifmap db. Without it, when a delete comes and we don't find it in our cache, we would not delete if from ifmap.
Also added a unit test case to catch this in future
Closes-Bug: 1355016

Change-Id: I9e8d8ba12f3ec970f830062bd7788d770a2055c0
Merge "For symmetrical links, we need to maintain links both ways in our cache of ifmap db. Without it, when a delete comes and we don't find it in our cache, we would not delete if from ifmap. Also added a unit test case to catch this in future Closes-Bug: 1355016"