Schema change to link loadbalancer pool to VMI

Add a link from loadbalancer pool to virtual machine interface(VMI).
VMI is linked to a logical interface of a physical router where the
configuration is stored.

Change-Id: I1f708e12ad0bef87c33da34b189d1c86574c4b81
Closes-Bug: #1381775
Merge "Schema change to link loadbalancer pool to VMI"