selftests/net: reduce xfrm_policy test time

The check_random_order test add/get plenty of xfrm rules, which consume
a lot time on debug kernel and always TIMEOUT. Let's reduce the test
loop and see if it works.
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://lore.kernel.org/r/20240514095227.2597730-1-liuhangbin@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/xfrm_policy.sh

@@ -293,7 +293,7 @@ check_random_order()
 	local ns=$1
 	local log=$2
 
-	for i in $(seq 100); do
+	for i in $(seq 50); do
 		ip -net $ns xfrm policy flush
 		for j in $(seq 0 16 255 | sort -R); do
 			ip -net $ns xfrm policy add dst $j.0.0.0/24 dir out priority 10 action allow
@@ -306,7 +306,7 @@ check_random_order()
 		done
 	done
 
-	for i in $(seq 100); do
+	for i in $(seq 50); do
 		ip -net $ns xfrm policy flush
 		for j in $(seq 0 16 255 | sort -R); do
 			local addr=$(printf "e000:0000:%02x00::/56" $j)