tests: Skip a sflow test for Windows.

AT_XFAIL_IF cannot be used here because it lets the tests
run first and then say that the failure is expected. In this
particular test, the utilities simply hang blocking all
other tests. So use AT_SKIP_IF instead.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
Acked-by: Nithin Raju <nithin@vmware.com>

tests/ofproto-dpif.at

@@ -4548,6 +4548,7 @@ CHECK_SFLOW_SAMPLING_PACKET([[[::1]]], [IPv6])
 
 dnl Test sFlow LAG structures
 AT_SETUP([ofproto-dpif - sFlow LACP structures])
+AT_SKIP_IF([test "$IS_WIN32" = "yes"])
 OVS_VSWITCHD_START([dnl
 		    add-bond br0 bond p1 p2 --				\
 		    set Port bond lacp=active bond-mode=active-backup	\