When using faketime, only run the scavenger for one loop.
It tries to run for 1 ms, but with faketime that calculation fails.
Prohibit write barriers in the faketime write function, in case
the GC wants to print something (e.g., with GODEBUG=gctrace=1).
Fixes #49614
Change-Id: Iab5097fe78b6e0032ea8b493088264dfb25013c6
Reviewed-on: https://go-review.googlesource.com/c/go/+/364757
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org> Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Go Bot <gobot@golang.org>