merge branch 'pr-1867'
merge branch 'pr-1867'

  Revert "libcontainer/rootfs_linux: minor cleanup"

LGTMs: d1134a78e2bf26a0abd6c50d47e304ac27e7ea97@cyphar
Closes #1867

mYmNeo/runc,xiaochenshen/runc,adrianreber/runc,laijs/runc,laijs/runc,xiaochenshen/runc,kolyshkin/runc,mikebrow/runc,kolyshkin/runc,dqminh/runc,rhatdan/runc,crosbymichael/runc,justincormack/runc,rhatdan/runc,crosbymichael/runc,dqminh/runc,opencontainers/runc,estesp/runc,mheon/runc,opencontainers/runc,xiaochenshen/runc,kolyshkin/runc,mheon/runc,opencontainers/runc,justincormack/runc,estesp/runc,laijs/runc,dqminh/runc,mikebrow/runc,adrianreber/runc,mheon/runc,dqminh/runc,opencontainers/runc,kolyshkin/runc,rhatdan/runc,justincormack/runc,mYmNeo/runc,cyphar/runc,adrianreber/runc,cyphar/runc,mYmNeo/runc,cyphar/runc,crosbymichael/runc,estesp/runc,rhatdan/runc,mikebrow/runc