selftests/net: convert sctp_vrf.sh to run it in unique namespace

Here is the test result after conversion.

]# ./sctp_vrf.sh
Testing For SCTP VRF:
TEST 01: nobind, connect from client 1, l3mdev_accept=1, Y [PASS]
...
TEST 12: bind vrf-2 & 1 in server, connect from client 1 & 2, N [PASS]
***v6 Tests Done***

Acked-by: David Ahern <[e-mail]>
Reviewed-by: Xin Long <[e-mail]>
Signed-off-by: Hangbin Liu <[e-mail]>
Signed-off-by: Paolo Abeni <[e-mail]>

tools/testing/selftests/net/sctp_vrf.sh

···
 #                                                  SERVER_NS
 #       CLIENT_NS2 (veth1) <---> (veth2) -> vrf_s2
 
-CLIENT_NS1="client-ns1"
-CLIENT_NS2="client-ns2"
+source lib.sh
 CLIENT_IP4="10.0.0.1"
 CLIENT_IP6="2000::1"
 CLIENT_PORT=1234
 
-SERVER_NS="server-ns"
 SERVER_IP4="10.0.0.2"
 SERVER_IP6="2000::2"
 SERVER_PORT=1234
···
 setup() {
 	modprobe sctp
 	modprobe sctp_diag
-	ip netns add $CLIENT_NS1
-	ip netns add $CLIENT_NS2
-	ip netns add $SERVER_NS
+	setup_ns CLIENT_NS1 CLIENT_NS2 SERVER_NS
 
 	ip net exec $CLIENT_NS1 sysctl -w net.ipv6.conf.default.accept_dad=0 2>&1 >/dev/null
 	ip net exec $CLIENT_NS2 sysctl -w net.ipv6.conf.default.accept_dad=0 2>&1 >/dev/null
···
 
 cleanup() {
 	ip netns exec $SERVER_NS pkill sctp_hello 2>&1 >/dev/null
-	ip netns del "$CLIENT_NS1"
-	ip netns del "$CLIENT_NS2"
-	ip netns del "$SERVER_NS"
+	cleanup_ns $CLIENT_NS1 $CLIENT_NS2 $SERVER_NS
 }
 
 wait_server() {