Merge pull request #21644 from markdroth/pf_reset_backoff_test_fix

Increase test timeout to avoid flakiness.

test/cpp/end2end/client_lb_end2end_test.cc

@@ -630,9 +630,11 @@ TEST_F(ClientLbEnd2endTest, PickFirstResetConnectionBackoff) {
       channel->WaitForConnected(grpc_timeout_milliseconds_to_deadline(10)));
   // Reset connection backoff.
   experimental::ChannelResetConnectionBackoff(channel.get());
-  // Wait for connect.  Should happen ~immediately.
+  // Wait for connect.  Should happen as soon as the client connects to
+  // the newly started server, which should be before the initial
+  // backoff timeout elapses.
   EXPECT_TRUE(
-      channel->WaitForConnected(grpc_timeout_milliseconds_to_deadline(10)));
+      channel->WaitForConnected(grpc_timeout_milliseconds_to_deadline(20)));
   const gpr_timespec t1 = gpr_now(GPR_CLOCK_MONOTONIC);
   const grpc_millis waited_ms = gpr_time_to_millis(gpr_time_sub(t1, t0));
   gpr_log(GPR_DEBUG, "Waited %" PRId64 " milliseconds", waited_ms);