osd/ReplicatedPG: set reply versions on dup op ACK

All other MOSDOpReply creators do this, with the exception of the pg
op.

Fixes: #6222
Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Greg Farnum <greg@inktank.com>
osd/ReplicatedPG: set reply versions for pg ops (PGLS)

Returning the current version for the pgid and last_user_version makes
some sense here.

Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Greg Farnum <greg@inktank.com>