scripts: tests: Removal of straggling folders

Current blacbox tests leave two folders,
OUT_DIR and TEST_DIR after they are finished.
Unit tests create two further folders,
mock_testsuite and demo_board_2.
This change deletes them appropriately.

Additionally, the created twister-out* folders in blackbox tests are
moved to a temp directory and removed after every test.

Signed-off-by: Lukasz Mrugala <lukaszx.mrugala@intel.com>