selftests/net/lib: no need to record ns name if it already exist

There is no need to add the name to ns_list again if the netns already
recoreded.

Fixes: 25ae948 ("selftests/net: add lib.sh")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: liuhangbin

tools/testing/selftests/net/lib.sh

@@ -127,15 +127,17 @@ setup_ns()
 	local ns=""
 	local ns_name=""
 	local ns_list=""
+	local ns_exist=
 	for ns_name in "$@"; do
 		# Some test may setup/remove same netns multi times
 		if unset ${ns_name} 2> /dev/null; then
 			ns="${ns_name,,}-$(mktemp -u XXXXXX)"
 			eval readonly ${ns_name}="$ns"
+			ns_exist=false
 		else
 			eval ns='$'${ns_name}
 			cleanup_ns "$ns"
-
+			ns_exist=true
 		fi
 
 		if ! ip netns add "$ns"; then
@@ -144,7 +146,7 @@ setup_ns()
 			return $ksft_skip
 		fi
 		ip -n "$ns" link set lo up
-		ns_list="$ns_list $ns"
+		! $ns_exist && ns_list="$ns_list $ns"
 	done
 	NS_LIST="$NS_LIST $ns_list"
 }