affile: fixed flush_lines/fsync option passing

Due to a refactoring issue, the argument ordering of flush_lines()
and fsync() options were mismatched with the function implementation.

The defaults remained the same, however setting flush_lines() enabled
fsync() and setting fsync set flush_lines() to 1.

This bug was introduced in 3.4.

Signed-off-by: Balazs Scheidler <bazsi@balabit.hu>