[grpclb_e2e_test] fix flake in SwapChildPolicy test

test/cpp/end2end/grpclb_end2end_test.cc

@@ -985,18 +985,12 @@ TEST_F(GrpclbEnd2endTest, SwapChildPolicy) {
   // Check that all requests went to the first backend.  This verifies
   // that we used pick_first instead of round_robin as the child policy.
   EXPECT_EQ(backends_[0]->service().request_count(), kNumRpcs);
-  for (size_t i = 1; i < backends_.size(); ++i) {
-    EXPECT_EQ(backends_[i]->service().request_count(), 0UL);
-  }
+  EXPECT_EQ(backends_[1]->service().request_count(), 0UL);
   // Send new resolution that removes child policy from service config.
   SetNextResolutionDefaultBalancer();
+  // We should now be using round_robin, which will send traffic to all
+  // backends.
   WaitForAllBackends();
-  CheckRpcSendOk(kNumRpcs, 3000 /* timeout_ms */, true /* wait_for_ready */);
-  // Check that every backend saw the same number of requests.  This verifies
-  // that we used round_robin.
-  for (size_t i = 0; i < backends_.size(); ++i) {
-    EXPECT_EQ(backends_[i]->service().request_count(), 2UL);
-  }
   // The balancer got a single request.
   EXPECT_EQ(1U, balancer_->service().request_count());
   // and sent a single response.