stream: workaround native network stack drops
stream: workaround native network stack drops

The native network stack expects that stream::produce() return a
ready, unfailed future in order to push the next packet.  However
commit 23f4faeea516426ba ("stream: use a smaller stick for failed
producers") adds a .then_wrapped() call, which sometimes converts
a ready furure to an unready one (due to max_inlined_continuations).

While this needs to be fixed in a better way, for now work around
it by detecting that the future is ready and not failed, and thus
the then_wrapped() call will have no effect, and returning
immediately.

sjperkins/seastar,syuu1228/seastar,acbellini/seastar,kjniemi/seastar,sjperkins/seastar,acbellini/seastar,xtao/seastar,linearregression/seastar,norcimo5/seastar,scylladb/seastar,dwdm/seastar,koolhazz/seastar,flashbuckets/seastar,printedheart/seastar,avikivity/seastar,shyamalschandra/seastar,bowlofstew/seastar,scylladb/seastar,flashbuckets/seastar,joerg84/seastar,xtao/seastar,leejir/seastar,jonathanleang/seastar,linearregression/seastar,tempbottle/seastar,scylladb/scylla-seastar,joerg84/seastar,dwdm/seastar,dwdm/seastar,xtao/seastar,bowlofstew/seastar,dreamsxin/seastar,wildinto/seastar,cloudius-systems/seastar,stamhe/seastar,wildinto/seastar,norcimo5/seastar,jonathanleang/seastar,dreamsxin/seastar,stamhe/seastar,hongliangzhao/seastar,acbellini/seastar,syuu1228/seastar,syuu1228/seastar,cloudius-systems/seastar,chunshengster/seastar,tempbottle/seastar,norcimo5/seastar,cloudius-systems/seastar,jonathanleang/seastar,hongliangzhao/seastar,printedheart/seastar,scylladb/scylla-seastar,avikivity/seastar,kjniemi/seastar,bowlofstew/seastar,anzihenry/seastar,koolhazz/seastar,hongliangzhao/seastar,printedheart/seastar,flashbuckets/seastar,sjperkins/seastar,chunshengster/seastar,kjniemi/seastar,leejir/seastar,scylladb/seastar,shyamalschandra/seastar,linearregression/seastar,koolhazz/seastar,anzihenry/seastar,stamhe/seastar,joerg84/seastar,shyamalschandra/seastar,anzihenry/seastar,avikivity/seastar,scylladb/scylla-seastar,dreamsxin/seastar,wildinto/seastar,tempbottle/seastar,chunshengster/seastar,leejir/seastar