P2P: Clear p2p->ssid_set on flush

It was possible for the previously set SSID to remain in place between
test cases (e.g., in sequence "p2ps_connect_adv_go_persistent
p2p_set_ssid_postfix") and the P2P SSID postfix not getting used
properly. Make this less likely to occur by clearing the old SSID in
p2p_flush().

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

src/p2p/p2p.c

@@ -2987,6 +2987,7 @@ void p2p_flush(struct p2p_data *p2p)
 	p2p_free_sd_queries(p2p);
 	os_free(p2p->after_scan_tx);
 	p2p->after_scan_tx = NULL;
+	p2p->ssid_set = 0;
 }