ose: Always yield after leader update

It is possible to end up in a state where we are "spinning"
around update leader without blocking in there and then we
can starve other schedulers running on the same core.

Ideally we would only yield if there was no block in update leader
but it is quite hard to know that, so we always yield instead. If
that becomes a performance issue we'll have to look at it later.
ose: Fix a bunch of compiler warnings
ose: Implement ose_yield as inlineable
ose: Use ppdata for storing own tid