Cleanup and fixes regarding bidirectional search and the test.sh files:

Cleanup and fixes regarding bidirectional search and the test.sh files:

- removed set_entries_head/tail from DQ entry (no longer needed, using vrh->dsq_head/tail for everything)
- removed no longer required vrh->root_set (not working with forward search anyways as there are multiple root sets)
- implemented cleanup for the dq entries in the queue_entries_head list of ds entries
- added the part in cleanup handling the subject_attribute/_len to might help solve the last valgrind error (didnt work)
- changed the way the ds_entry are inserted in the vrh->dsq_.. list: Now after creation of EVERY ds_entry it is inserted
--> This solved an error resulting from uncanceled lookup_response handles
- changed the test_credential...bi..sh files:
	+ "- -" at the end of the collect statement, required for MacOS
	+ fixed cleanup at the end to correctly remove entries from GNS