Commit 52275e92 made a small change in generic device classification
based on sysObjectID for devices that don't report Layer1 - Layer3
capabilities, in order to skip generic assignment if a more specific
class had already been determined. However this change contained an
error causing generic classification to fail.
Nex fix explicitly checks if class isn't more specific than SNMP::Info
before attempting to classify based on sysObjectID.
The test_class.pl script refused to test devices that don't implement
sysServices. Since SNMP::Info has been modified to check connectivity
by testing sysDescr as well, test_class.pl should follow that behaviour.