NMS-6832 Cleaner Snmp code
- SnmpObjId could not correctly handle oids with large unsigned int values
- Fix MockSnmpValueFactory and ProperitesBackedManagedObject to handle snmpwalk output containing text like
  Wrong Type (should be XXXXX): INTEGER: 0
- Extended JUnitSnmpAgent and JUnitSnmpAgents to have a 'forceMockStrategy' flag
- Changed the linkd Nms10205aTest test to force the MockStrategy to avoid problems with agents
  so as to take the socket reponsiveness and such out of the equation