rtnetlink: fix Link ListByKind response

[boussole]

the linux kernel handles a RTM_GETLINK request even in case of incorrent kind filter. if it finds requested kind it responds with a list of this kind of links and marks every message in a response by NLM_F_DUMP_FILTERED flag. Otherwise it sends all available links w/o NLF_F_DUMP_FILTERED. So, looks much better to return to a callee empty link list if there are no links of requested kind.