This commit partially reverts r273641 which introduced the leak.
It did so to accomodate for some consumers of traverse() that expected
the starting vnode to stay as-is. But that introduced the leak in the
case when a mounted filesystem was found and its root vnode was
returned.
r299914 removed the troublesome consumers and now there is no reason to
keep the starting vnode. So, now the new rules are:
- if there is no mounted filesystem, then nothing is changed
- otherwise the starting vnode is always released
- the root vnode of the mounted filesystem is returned locked and
referenced in the case of success
MFC after: 5 weeks
X-MFC after: r299914