Fix QuicEndpointTest failure when using QUIC-over-TLS.

gfe-relnote: n/a (test-only change)
PiperOrigin-RevId: 298462380
Change-Id: I4e3a9766fd80d66eba207442ccab9124c46591f8

quic/test_tools/simulator/quic_endpoint.cc

diff --git a/quic/test_tools/simulator/quic_endpoint.cc b/quic/test_tools/simulator/quic_endpoint.cc
index 6ec84b0..c908f98 100644
--- a/quic/test_tools/simulator/quic_endpoint.cc
+++ b/quic/test_tools/simulator/quic_endpoint.cc
@@ -50,6 +50,7 @@
                               std::make_unique<NullDecrypter>(perspective));
   }
   connection_->SetDefaultEncryptionLevel(ENCRYPTION_FORWARD_SECURE);
+  connection_->OnHandshakeComplete();
   if (perspective == Perspective::IS_SERVER) {
     // Skip version negotiation.
     test::QuicConnectionPeer::SetNegotiatedVersion(connection_.get());