[NETNS]: Add namespace parameter to ip_options_compile.

ip_options_compile uses inet_addr_type which requires a namespace. The
packet argument is optional, so parameter is the only way to obtain
it. Pass the init_net there for now.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>