journal: wait for in flight advance sets on stopping recorder

journal: wait for in flight advance sets on stopping recorder

Before object overflow detection optimization (83461c42b) the
overflow was detected when trying to send data, so when an object
set was advanced we always had some data and flush always
completed later. But now we detect overflow on client side, it
may happen when buffer is empty and flush may complete
when "advance object set" is still in flight.

Signed-off-by: Mykola Golub <mgolub@suse.com>