mgcp/rtp: Add flag to disable RTP output

This patch make it possible to have a valid endpoint that drops all
outgoing RTP packets. The number of dropped packets is shown by the
VTY 'show mgcp' command. By default, this feature is disabled. To
enable packet dropping, the corresponding output_enabled field must
be set to 0.

Ticket: OW#1044
Sponsored-by: On-Waves ehf
diff --git a/openbsc/src/libmgcp/mgcp_protocol.c b/openbsc/src/libmgcp/mgcp_protocol.c
index ddec44d..95f3910 100644
--- a/openbsc/src/libmgcp/mgcp_protocol.c
+++ b/openbsc/src/libmgcp/mgcp_protocol.c
@@ -1178,6 +1178,7 @@
 
 	end->packets = 0;
 	end->octets = 0;
+	end->dropped_packets = 0;
 	memset(&end->addr, 0, sizeof(end->addr));
 	end->rtp_port = end->rtcp_port = 0;
 	end->payload_type = -1;
@@ -1191,6 +1192,7 @@
 	end->frames_per_packet  = 0; /* unknown */
 	end->packet_duration_ms = DEFAULT_RTP_AUDIO_PACKET_DURATION_MS;
 	end->rate               = DEFAULT_RTP_AUDIO_DEFAULT_RATE;
+	end->output_enabled	= 1;
 }
 
 static void mgcp_rtp_end_init(struct mgcp_rtp_end *end)