Update load balancer tests to use allocation pools

Sometimes LB fixed IPs can overlap with IPs which
portprober picked up from the same network.
Using allocation pools and different IP ranges for
static and dynamic IP assignement can solve the problem

Related-prod: PRODX-49726

Change-Id: Ic8246ef4addf8fd1a0d4654f1613d815350c482a
1 file changed