ipvs: supply a valid 0 address to ip_vs_conn_new()

ip_vs_conn_new expects a union nf_inet_addr as the type for its address
parameters, not a plain integer.

This problem was detected by sparse.

make C=1
  CHECK   net/ipv4/ipvs/ip_vs_core.c
net/ipv4/ipvs/ip_vs_core.c:469:9: warning: Using plain integer as NULL pointer

Acked-by: Sven Wegener <sven.wegener@stealer.net>
Acked-by: Julius Volz <juliusv@google.com>
Signed-off-by: Simon Horman <horms@verge.net.au>