memleak: fix all libosmocore callers of gsmtap_sendmsg() to free on failure

gsmtap_sendmsg() does not free the msgb if it returns a failure rc, so the
callers must check the rc and free the msg.

Change-Id: I7cf64ed9b14247298ed8b4ab8735627f8235a499
diff --git a/src/gsmtap_util.c b/src/gsmtap_util.c
index 962782b..b21c690 100644
--- a/src/gsmtap_util.c
+++ b/src/gsmtap_util.c
@@ -303,6 +303,7 @@
 		unsigned int len)
 {
 	struct msgb *msg;
+	int rc;
 
 	if (!gti)
 		return -ENODEV;
@@ -312,7 +313,10 @@
 	if (!msg)
 		return -ENOMEM;
 
-	return gsmtap_sendmsg(gti, msg);
+	rc = gsmtap_sendmsg(gti, msg);
+	if (rc)
+		msgb_free(msg);
+	return rc;
 }
 
 /*! send a message from L1/L2 through GSMTAP.