tests: Capture the output of netopeer2-server

Change-Id: I78c097db22ab360718a9d128d81ce9ad32353071
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 92ab37f..be7f96e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -270,6 +270,7 @@
 
         file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/test_repositories)
         file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/test_sockets)
+        file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/test_netopeer_outputs)
     endif()
 
     configure_file(${CMAKE_CURRENT_SOURCE_DIR}/tests/yang_access_test_vars.hpp.in ${CMAKE_CURRENT_BINARY_DIR}/yang_access_test_vars.hpp @ONLY)