Previously, the number of endpoints in a locality would skew how much
traffic was sent to that locality. Also, if endpoints in localities had
wildly different weights, that would impact cross-locality weighting.

For example, consider:
  LocalityA weight=1 endpointWeights=[100, 100, 100, 100]
  LocalityB weight=1 endpointWeights=[1]

The endpoint in LocalityB should have an endpoint weight that is half
the total sum of endpoint weights, in order to receive half the traffic.
But the multiple endpoints in LocalityA would cause it to get 4x the
traffic and the endpoint weights in LocalityA causes them to get 100x
the traffic.

See gRFC A113