core/reactor: Throw the right error code when connect() fails
core/reactor: Throw the right error code when connect() fails

We threw errno, which is stale (likely E_INPROGRESS), instead of the
actual value of SO_ERROR.

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