s3: smbd: Add async internals of reply_close().

s3: smbd: Add async internals of reply_close().

Waits until all aio requests on the closing fsps
before returning to the client.

Slightly modified version of the existing async
reply_close code, updated to use the wait_queue
pattern standardized in reply_tdis, reply_ulogoffX
and reply_exit.

Done this way (commented out) so it is a clean
diff and it's clear what is being added.

The next commit will remove the old version.

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>