ipvs: change some __constant_htons() to htons()

Change __contant_htons() to htons() in the IPVS code when not in an
initializer.

-Brian

Signed-off-by: Brian Haley <brian.haley@hp.com>
Acked-by: Julius Volz <juliusv@google.com>
Signed-off-by: Simon Horman <horms@verge.net.au>