Add contract notes for dns_requestmgr_{attach,detach}().
Add contract notes for dns_requestmgr_{attach,detach}().

pecharmin/bind9,pecharmin/bind9,pecharmin/bind9,pecharmin/bind9,pecharmin/bind9,each/bind9-collab,each/bind9-collab,each/bind9-collab,each/bind9-collab,pecharmin/bind9,each/bind9-collab,each/bind9-collab