Excess contention in DummyLoadBalancer.pickTransport

[carl-mastrangelo]

      flat  flat%   sum%        cum   cum%
    27.54s  0.72% 97.66%    959.60s 25.18%  io.grpc.DummyLoadBalancerFactory$DummyLoadBalancer.pickTransport DummyLoadBalancerFactory.java:90