Fix oid-sorting in the snmp-adaptor

Sorting of oids still sucks somewhat. Order is currently .1.2.3.1, .1.2.3.10, .1.2.3.2, .1.2.3.3 which makes getnext return less data than desired

Also take into account, that management systems might ask for a node and then want to walk the subtree by issuing get and getNext requests. So if a request for a node fails and this node was no leaf (.0 ending), try to get the subnode with the smallest "sub-oid".