bitbake: persist_data: Avoid fsync() calls

bitbake: persist_data: Avoid fsync() calls

If the power were to fail, it doesn't matter to us much if the data
makes it to disk or not, we'd have other problems. However an fsync()
call on a multi build autobuilder is painful so lets avoid them.

This is particularly true in this case if a timeout causes a reconnect
during a build.

(Bitbake rev: ec28256ac2a30f047585e8f61200d764bc295ded)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>