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

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

Waits until all aio requests on all fsp's owned by this
vuid are finished before returning to the client.

Charges the profile time in the done function. Not strictly
correct but better than the other SMB1 async code that
double-charges profiling in both send and done at the
moment.

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

A later commit will remove the old synchronous version.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14301

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