silent_call: remove unfinished fuzzer interface

Remove the fuzzer interface that was partially implemented in
gsm_04_08.c and silent_call.c is causing problems when an
SMS is sent during an active silent call. The reason for this
is that gsm0408_dispatch() in gsm_04_08.c would decide to
rout all uplink traffic to silent_call_rx() in silent_call.c.
silent_call_rx() is a stub function that discards the data.

This patch removes the fuzzer interface code by placing ifdefs
around it, so that it can be re-activated by experimentators.

Change-Id: Id500197d58663b3f4b1756136343670388b0a4bc
diff --git a/openbsc/src/libmsc/gsm_04_08.c b/openbsc/src/libmsc/gsm_04_08.c
index be43956..3cc86ba 100644
--- a/openbsc/src/libmsc/gsm_04_08.c
+++ b/openbsc/src/libmsc/gsm_04_08.c
@@ -3958,8 +3958,10 @@
 	OSMO_ASSERT(msg);
 
 	LOGP(DRLL, LOGL_DEBUG, "Dispatching 04.08 message, pdisc=%d\n", pdisc);
+#if 0
 	if (silent_call_reroute(conn, msg))
 		return silent_call_rx(conn, msg);
+#endif
 
 	switch (pdisc) {
 	case GSM48_PDISC_CC: