ipc/tcp stream tests: use dup() to avoid confusion and hang in teardown

This was observed only in the select poller, but the behavior of having
the same file descriptor registered in the poller more than once is undefined.

src/platform/ipc_stream_test.c

@@ -133,6 +133,11 @@ test_ipc_listen_activation(void)
 	NUTS_PASS(nng_stream_dialer_alloc(&d, addr));
 
 	NUTS_PASS(nng_stream_listener_get_int(l1, NNG_OPT_LISTEN_FD, &fd));
+	fd = dup(fd);
+	// dupe this because we need to separate the file descriptors to
+	// prevent confusion when we clean up (only one FD can be registered at
+	// a time!)
+	NUTS_ASSERT(fd >= -1);
 	NUTS_PASS(nng_stream_listener_alloc(&l2, addr));
 	NUTS_PASS(nng_stream_listener_set_int(l2, NNG_OPT_LISTEN_FD, fd));
 	nng_stream_dialer_dial(d, aio2);

src/platform/tcp_stream_test.c

@@ -115,10 +115,6 @@ test_tcp_stream(void)
 	NUTS_TRUE(sa2.s_in.sa_addr == sa.s_in.sa_addr);
 	NUTS_TRUE(sa2.s_in.sa_port == sa.s_in.sa_port);
 
-	nng_stream_listener_close(l);
-	nng_stream_dialer_close(d);
-	nng_stream_listener_stop(l);
-	nng_stream_dialer_stop(d);
 	nng_stream_listener_free(l);
 	nng_stream_dialer_free(d);
 	nng_aio_free(aio1);
@@ -214,6 +210,12 @@ test_tcp_listen_activation(void)
 	NUTS_PASS(nng_stream_dialer_alloc(&d, url));
 
 	NUTS_PASS(nng_stream_listener_get_int(l1, NNG_OPT_LISTEN_FD, &fd));
+	fd = dup(fd);
+	// dupe this because we need to separate the file descriptors to
+	// prevent confusion when we clean up (only one FD can be registered at
+	// a time!)
+	NUTS_ASSERT(fd >= -1);
+
 	NUTS_PASS(nng_stream_listener_alloc(&l2, "tcp4://"));
 	NUTS_PASS(nng_stream_listener_set_int(l2, NNG_OPT_LISTEN_FD, fd));
 	nng_stream_dialer_dial(d, aio2);