syscall: move TestForegroundSignal create call out of goroutine
That way the skip takes effect.
Also ignore the result of calling TIOCSPGRP when cleaing up TestForeground.
It has started to fail for some reason, and the result doesn't matter.
Also call TIOCSPGRP to clean up in TestForegroundSignal.
For #37217
Change-Id: I2e4282d7d91ad9a198eeb12cef01c2214c2a98c2
Reviewed-on: https://go-review.googlesource.com/c/go/+/314271
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org> Reviewed-by: Cherry Zhang <cherryyz@google.com>