add integration test for getnext from broker

CMakeModules/testing_cpp.cmake

tests/worker/CMakeLists.txt

tests/worker/next_multithread_broker/CMakeLists.txt

tests/worker/next_multithread_broker/check_linux.sh

tests/worker/next_multithread_broker/check_windows.bat

...orker/next_multithread_broker/next_multithread_broker.cpp

tests/worker/next_multithread_folder/CMakeLists.txt

tests/worker/next_multithread_folder/cleanup_linux.sh

tests/worker/next_multithread_folder/cleanup_windows.bat

...orker/next_multithread_folder/next_multithread_folder.cpp

tests/worker/next_multithread_folder/setup_linux.sh

tests/worker/next_multithread_folder/setup_windows.bat

worker/api/cpp/unittests/test_server_broker.cpp