[release-branch.go1.15] syscall: fix TestGroupCleanupUserNamespace test failure on Fedora
For #46752
Fixes #46768
Change-Id: I2eaa9d15fac4e859e18191fcf1372e5be94899df
GitHub-Last-Rev:
f533c37ff9d259e307b200a01e3606bfaff10464
GitHub-Pull-Request: golang/go#46753
Reviewed-on: https://go-review.googlesource.com/c/go/+/328069
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>