Fix two bugs in the lockf code. The first one is a missing reinitialization

Fix two bugs in the lockf code. The first one is a missing reinitialization
of the type field if an existing lock is extended to cover a bigger range
with a different type. The second is related to the problem reported by
Joerg Anslik <joerg@anslik.de> and comes from capturing real uid changes,
but using the effective uid userinfo structure for the accounting.