Remove the sticky Hop-by-Hop options header by calling setsockopt()
for IPV6_HOPOPTS with a zero option length, per RFC3542.

Routing header and Destination options header does the same as
Hop-by-Hop options header.
Signed-off-by: NShan Wei <shanwei@cn.fujitsu.com>
Acked-by: NYOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>