macos: bulkstat redux

macos: bulkstat redux

simplify the logic which can require sleeps in various vcache
resolution paths. instead of the two-pass system we had before,
just guess using the even/odd hack what type a vnode will be.
if a vnode turns out to be a link and thus we are wrong, we
do a fixup later. other callers who "race" with bulkstat
(which is a supported feature, otherwise you'd have to block
callbacks) will also call through a fixup to get the correct
backing vnode type. this is necessary as the KPI doesn't
let us change the type of a vnode after it's been created.

side effect: eliminate many of the ugly cases where we had been
sleeping waiting for a vnode to be finalized even before bulkstat.

Change-Id: Ib888fa5577d48354725ea72305765e4341bc2366
Reviewed-on: http://gerrit.openafs.org/4677
Tested-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>