os/signal: increase settle time in tests
I noticed a timeout in TestIgnore in
https://build.golang.org/log/
52d83a72f3a5ea9a16eb5d670c729694144f9624,
which suggests that the settle time is currently set too low.
I've also added a check for the same GO_TEST_TIMEOUT_SCALE used in
TestTerminalSignal, so that if this builder remains too slow we can
increase the builder's scale factor rather than the test's baseline
running time.
Updates #33174
Change-Id: I18b10eaa3bb5ae2f604300aedaaf6f79ee7ad567
Reviewed-on: https://go-review.googlesource.com/c/go/+/227649
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>