main/lxc: backport file descriptor patch

without it, you'll find that /proc/1/fd/14 points to
/proc/1234/status. This breaks some software, like Anbox
(https://github.com/anbox/anbox/issues/1397).
7 jobs for !6713 with lxc4-anbox in 5 minutes and 40 seconds (queued for 2 seconds)
latest detached
Status Job ID Name Coverage
  Lint
passed #91677
x86_64 docker-alpine
lint

00:00:22

 
  Build
passed #91682
aarch64 ci-build docker-alpine
build-aarch64

00:01:34

passed #91683
armv7 ci-build docker-alpine
build-armv7

00:01:54

passed #91681
ppc64le ci-build docker-alpine
build-ppc64le

00:04:27

passed #91680
s390x ci-build docker-alpine
build-s390x

00:02:29

passed #91679
x86 ci-build docker-alpine
build-x86

00:00:49

passed #91678
x86_64 ci-build docker-alpine
build-x86_64

00:00:53