Fixing Bug 1900 and 1908

Updating LBaaSPoolMemberHandler to process member add/delete correctly.
Previously the rules were not pushed or deletede properly.

Also committing the index subtraction in LoadBalancerService that was
not merged properly in the earlier commit.

Change-Id: If367895407a284333a0438ae76312063fe3d8ded
Signed-off-by: Srini Seetharaman <srini.seetharaman@gmail.com>