The status enumeration is simple enough now that we can
view it as a bit set instead. Switch to a bit set, freeing up
the remaining bits for use in followup work to allow
garbage-collecting timers.
[This is one CL in a refactoring stack making very small changes
in each step, so that any subtle bugs that we miss can be more
easily pinpointed to a small change.]
Change-Id: I5f331fe3db1b5cb52f8571091f97f8ba029f3ac9
Reviewed-on: https://go-review.googlesource.com/c/go/+/564130
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Ian Lance Taylor <iant@google.com>