Only send ping requests to client that support it

tests/functionaltests/test_ping.h

@@ -1,3 +1,5 @@
-void ping_multiple(void **state);
-void ping_not_supported(void **state);
-void ping_responds(void **state);
+void ping_server(void **state);
+void ping_server_not_supported(void **state);
+void ping_responds_to_server_request(void **state);
+void ping_jid(void **state);
+void ping_jid_not_supported(void **state);