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/logging_gsmtap.c b/src/logging_gsmtap.c
index cb379b0..c53a0ab 100644
--- a/src/logging_gsmtap.c
+++ b/src/logging_gsmtap.c
@@ -103,7 +103,9 @@
 		return;
 	msgb_put(msg, rc);
 
-	gsmtap_sendmsg(target->tgt_gsmtap.gsmtap_inst, msg);
+	rc = gsmtap_sendmsg(target->tgt_gsmtap.gsmtap_inst, msg);
+	if (rc)
+		msgb_free(msg);
 }
 
 /*! Create a new logging target for GSMTAP logging