Merge 164850 - Seccomp-BPF: relax failure in probe process setup

Merge 164850 - Seccomp-BPF: relax failure in probe process setup

When we set-up the probe process to test seccomp-bpf availability, setting
a pipe on stderr can sometimes fail. Presumably if this descriptor is backed
by a file on a file system that will return an error on close().

We don't consider not being able to set-up the pipe on stderr as a fatal error
anymore.

BUG=152530
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/11300014

TBR=jln@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=166990