libcontainer: cgroups: fs: add cgroup path safety unit tests
libcontainer: cgroups: fs: add cgroup path safety unit tests

In order to avoid problems with security regressions going unnoticed,
add some unit tests that should make sure security regressions in cgroup
path safety cause tests to fail in runC.

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

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