Set packet type in quic_connection_test according to encryption levels.
Also have some other minor test changes.

gfe-relnote: n/a (test only change)
PiperOrigin-RevId: 238230970
Change-Id: I35cc161dc9e42468c3d87f951c9af9b74ee599fa

quic/core/quic_session_test.cc

diff --git a/quic/core/quic_session_test.cc b/quic/core/quic_session_test.cc
index a1b294b..915d31b 100644
--- a/quic/core/quic_session_test.cc
+++ b/quic/core/quic_session_test.cc
@@ -1139,6 +1139,8 @@
       .WillOnce(Invoke(
           connection_,
           &MockQuicConnection::ReallySendConnectivityProbingResponsePacket));
+  QuicConnectionPeer::SetLastHeaderFormat(connection_,
+                                          IETF_QUIC_SHORT_HEADER_PACKET);
   // Need to explicitly do this to emulate the reception of a PathChallenge,
   // which stores its payload for use in generating the response.
   connection_->OnPathChallengeFrame(