add a function to close the packet handler map

Close will close the underlying connection and wait until listen has
returned. While not strictly necessary in production use, this will fix
a few race conditions in our tests.

mock_packet_handler_manager_test.go

@@ -44,6 +44,18 @@ func (mr *MockPacketHandlerManagerMockRecorder) Add(arg0, arg1 interface{}) *gom
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Add", reflect.TypeOf((*MockPacketHandlerManager)(nil).Add), arg0, arg1)
 }
 
+// Close mocks base method
+func (m *MockPacketHandlerManager) Close() error {
+	ret := m.ctrl.Call(m, "Close")
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// Close indicates an expected call of Close
+func (mr *MockPacketHandlerManagerMockRecorder) Close() *gomock.Call {
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Close", reflect.TypeOf((*MockPacketHandlerManager)(nil).Close))
+}
+
 // CloseServer mocks base method
 func (m *MockPacketHandlerManager) CloseServer() {
 	m.ctrl.Call(m, "CloseServer")