mgcp: Avoid initing output without enabling osmux

Otherwise we end up in a weird state where we have timers set up but
osmux is still flagged as not enabled.

Change-Id: I15c3a1a6bdf2566b03d1d543d8d15e4117a53622
diff --git a/openbsc/src/libmgcp/mgcp_osmux.c b/openbsc/src/libmgcp/mgcp_osmux.c
index 69f1c66..0a4441c 100644
--- a/openbsc/src/libmgcp/mgcp_osmux.c
+++ b/openbsc/src/libmgcp/mgcp_osmux.c
@@ -447,10 +447,6 @@
 		return -1;
 	}
 
-	osmux_xfrm_output_init(&endp->osmux.out,
-			       (endp->osmux.cid * rtp_ssrc_winlen) +
-			       (random() % rtp_ssrc_winlen));
-
 	endp->osmux.in = osmux_handle_lookup(endp->cfg, addr, port);
 	if (!endp->osmux.in) {
 		LOGP(DMGCP, LOGL_ERROR, "Cannot allocate input osmux handle\n");
@@ -463,6 +459,10 @@
 		return -1;
 	}
 
+	osmux_xfrm_output_init(&endp->osmux.out,
+			       (endp->osmux.cid * rtp_ssrc_winlen) +
+			       (random() % rtp_ssrc_winlen));
+
 	switch (endp->cfg->role) {
 		case MGCP_BSC_NAT:
 			endp->type = MGCP_OSMUX_BSC_NAT;