message: In exploit_tests.cpp fix verack_tests
  We don't have to SendMessages when we're just checking for a
  disconnect.  Only when we check a ban do we have to do this.  Also
  make sure the nVersion is low enough that we don't trigger deserializing
  the PING message since we're sending an empty vRecv.
diff: @@ -190,23 +190,21 @@ BOOST_AUTO_TEST_CASE(verack_tests)
  vRecv1.clear();
  CNode::ClearBanned();
  CNode dummyNode4(INVALID_SOCKET, addr4, "", true);
  - dummyNode4.nVersion = MIN_PEER_PROTO_VERSION;
  + dummyNode4.nVersion = 1;
  dummyNode4.fSuccessfullyConnected = false;
  dummyNode4.tVersionSent = nStartTime;
  SetMockTime(nStartTime + VERACK_TIMEOUT); // should not disconnect if timeout not exceeded and no VERACK
  ProcessMessage(&dummyNode4, NetMsgType::PING, vRecv1, GetTime());
  - SendMessages(&dummyNode4);
  BOOST_CHECK(!dummyNode4.fDisconnect);
  vRecv1.clear();
  CNode::ClearBanned();
  CNode dummyNode4a(INVALID_SOCKET, addr4, "", true);
  - dummyNode4a.nVersion = MIN_PEER_PROTO_VERSION;
  + dummyNode4a.nVersion = 1;
  dummyNode4a.fSuccessfullyConnected = false;
  dummyNode4a.tVersionSent = nStartTime;
  SetMockTime(nStartTime + VERACK_TIMEOUT + 1); // should disconnect if timeout exceeded and no VERACK
  ProcessMessage(&dummyNode4a, NetMsgType::PING, vRecv1, GetTime());
  - SendMessages(&dummyNode4a);
  BOOST_CHECK(dummyNode4a.fDisconnect);
  }
  