lib/tsocket: optimize tdgram_recvfrom_done() into tdgram_recvfrom_send()

lib/tsocket: optimize tdgram_recvfrom_done() into tdgram_recvfrom_send()

For callers using tdgram_bsd_optimize_recvfrom() it is every useful
to know it data was already waiting in the socket.

In that case the result from tdgram_bsd_recvfrom_send() would
already report tevent_req_is_in_progress() as false.

But the result of tdgram_recvfrom_send() available to the
caller would see tevent_req_is_in_progress() reporting true.

With this change also the result of tdgram_recvfrom_send()
would report tevent_req_is_in_progress() as false,
which will be useful for callers, which would otherwise
set a timeout on the request.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>