Rackspace::Cloud::LoadBalancer may be in an immutable state just before
deleting as well (see change I46692f29b57a8c5db9a2dfab11ac5dc9ad631d45).
This adds retry logic to delete action as well.
Related-Bug: 140881
Change-Id: I41543fc1e0aee2c061862736f7fe544b01331b0a