Events: fixed setting of IP_BIND_ADDRESS_NO_PORT/SO_REUSEADDR.

The IP_BIND_ADDRESS_NO_PORT option is set on upstream sockets
if proxy_bind does not specify a port.  The SO_REUSEADDR option
is set on UDP upstream sockets if proxy_bind specifies a port.

Due to checking of the wrong port, IP_BIND_ADDRESS_NO_PORT was
never set, and SO_REUSEPORT was always set.