Wait for input after einprogress and ealready too. 

Accept and connect are called asynchronously. Because of this sendfile can sometimes return errno EINPROGRESS or EALREADY. The correct way to handle this is to wait until data is available. 

BTW I know you deprecated your sendfile repo, but because `file:sendfile` has a DOS problem in R15 and R16 this is still an important repo.