time: increase slop for TestTicker
time: increase slop for TestTicker

Also sleep a bit each time it fails, in case the system is overloaded.

Fixes #37332

Change-Id: Iabf3d0a27b5834c1e2a87c826b6206146b4f62c5
Reviewed-on: https://go-review.googlesource.com/c/go/+/313849
Trust: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>

CAFxX/go,golang/go,golang/go,CAFxX/go,golang/go,cloudflare/go,golang/go,cloudflare/go,CAFxX/go,golang/go,nawawi/go,cloudflare/go,nawawi/go,cloudflare/go,CAFxX/go,nawawi/go,nawawi/go,cloudflare/go,cloudflare/go,cloudflare/go,nawawi/go,golang/go,nawawi/go,CAFxX/go,CAFxX/go,nawawi/go,golang/go,CAFxX/go,nawawi/go,CAFxX/go,golang/go,cloudflare/go