init v4_address earlier

fix this problem:


>Traceback (most recent call last):
> File "/var/daes/lib/python2.7/site-packages/raven/base.py", line 549, in send_remote
>    transport.send(data, headers)
>  File "/var/daes/lib/python2.7/site-packages/raven/transport/udp.py", line 50, in send
>    addr_info = self._get_addr_info(host, int(port))
>  File "/var/daes/lib/python2.7/site-packages/raven/transport/udp.py", line 40, in _get_addr_info
>    return v4_addresses[0]
>UnboundLocalError: local variable 'v4_addresses' referenced before assignment