pgw: Don't wait for 10s timeout if starting a ping that takes 10s

rather, dynamically wait 5s longer than the theoretical time it
should take.

Change-Id: Ife2b7b8d03ee6808cfa73bb860cc63c46c451499
diff --git a/pgw/PGW_Tests.ttcn b/pgw/PGW_Tests.ttcn
index 22e32da..cf3b901 100644
--- a/pgw/PGW_Tests.ttcn
+++ b/pgw/PGW_Tests.ttcn
@@ -335,7 +335,7 @@
 	var charstring ping :="ping -c " & int2str(count) & " -i " & int2str(interval);
 	ping := ping & " -I " & f_inet_ntoa(g_ip4_addr);
 	ping := ping & " " & host;
-	f_start_prog_wait(ping);
+	f_start_prog_wait(ping, tout := int2float(5 + interval*count));
 }