stream: properly set exception
stream: properly set exception

The try / catch block is a thing of the past: it doesn't really work with
futures. The proper way to do it is with then_wrapped.

Signed-off-by: Glauber Costa <f8b79557d19b40666ebe336545a0b6178af65685@cloudius-systems.com>

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