CppunitTest_sd_import_tests: missing DoClose() call

This leaked two files in /tmp during every run.

Change-Id: I8dc0574c210925fa5d6704ffad9c106186a50151
std::set::find() is faster than plain std::find()

Change-Id: I11ca9474e4b6b751f0348b78b53abaa81682eaa6