- Check for EOF condition (remote has closed) before writing.

If we don't do this, then the write will still succeed even after the
remote has closed (half-closed in CLOSE_WAIT on our side), and the 2nd
write after will fail causing the previous event to be lost.
- Try forever to connect w/ exponential backoff
- remove a blank line
Merge pull request #657 from logstash/tcp-output-client-close-fix

Tcp output client remote-has-closed fix