fixed error check condition

inventory_provider/snmp.py

@@ -74,7 +74,7 @@ def walk(agent_hostname, community, base_oid):  # pragma: no cover
                 'snmp response pdu error %r at %r' % (
                     pduErrorIndication,
                     errorIndex and varBinds[int(errorIndex) - 1][0] or '?'))
-        if errorIndex == 0:
+        if errorIndex != 0:
             raise SNMPWalkError(
                 'sanity failure: errorIndex != 0, '
                 'but no error indication')