nsenter: simplify netlink parsing
nsenter: simplify netlink parsing

This just moves everything to one function so we don't have to pass a
bunch of things to functions when there's no real benefit. It also makes
the API nicer.

Signed-off-by: Aleksa Sarai <a8eb12d32d6ec07cdf737175ec7d4a0f1b4e1ee7@suse.de>

vbatts/runc,avagin/runc,coolljt0725/runc,laijs/runc,mikebrow/runc,adrianreber/runc,hqhq/runc,opencontainers/runc,nkwilson/runc,rajasec/runc,cloudfoundry-incubator/runc,maxamillion/runc,rajasec/runc,dqminh/runc,stefanberger/runc,mheon/runc,adrianreber/runc,kolyshkin/runc,docker/runc,opencontainers/runc,justincormack/runc,cloudfoundry-incubator/runc,kolyshkin/runc,mYmNeo/runc,adrianreber/runc,justincormack/runc,mYmNeo/runc,rhatdan/runc,sunyuan3/runc,cyphar/runc,estesp/runc,docker/runc,rhatdan/runc,mikebrow/runc,WeiZhang555/runc,jhowardmsft/runc,estesp/runc,shishir-a412ed/runc,crosbymichael/runc,mYmNeo/runc,keloyang/runc,jhowardmsft/runc,rhatdan/runc,xiaochenshen/runc,vbatts/runc,maxamillion/runc,nkwilson/runc,kolyshkin/runc,vbatts/runc,cyphar/runc,dqminh/runc,jhowardmsft/runc,maxamillion/runc,wking/runc,sunyuan3/runc,opencontainers/runc,rhatdan/runc,hqhq/runc,docker/runc,coolljt0725/runc,mheon/runc,crosbymichael/runc,crosbymichael/runc,coolljt0725/runc,wking/runc,rajasec/runc,avagin/runc,keloyang/runc,WeiZhang555/runc,shishir-a412ed/runc,stefanberger/runc,avagin/runc,dqminh/runc,stefanberger/runc,mheon/runc,WeiZhang555/runc,sunyuan3/runc,nkwilson/runc,xiaochenshen/runc,wking/runc,xiaochenshen/runc,mikebrow/runc,justincormack/runc,laijs/runc,keloyang/runc,kolyshkin/runc,cloudfoundry-incubator/runc,hqhq/runc,cyphar/runc,opencontainers/runc,dqminh/runc,estesp/runc,shishir-a412ed/runc,laijs/runc