ipvs: Remove unused variable "cs" from ip_vs_leave function.

This is to address the following warning during compilation time:

  net/netfilter/ipvs/ip_vs_core.c: In function ‘ip_vs_leave’:
  net/netfilter/ipvs/ip_vs_core.c:532: warning: unused variable ‘cs’

This variable is indeed no longer in use.

Signed-off-by: Krzysztof Wilczynski <krzysztof.wilczynski@linux.com>
Signed-off-by: Simon Horman <horms@verge.net.au>