osmo-msc: free the VTY talloc context on exit

This is a follow up change before enabling the track of NULL talloc
contexts. Since there is no other way to deinitialize libosmovty,
let's free its root context on exit. Otherwise one would see
lots of memory chunks on exit...

Change-Id: I278f85f023210de6b4626d4493d10d20996f606a

src/osmo-msc/msc_main.c

@@ -710,6 +710,9 @@ TODO: we probably want some of the _net_ ctrl commands from bsc_base_ctrl_cmds_i
 	talloc_report_full(tall_msc_ctx, stderr);
 	talloc_free(tall_msc_ctx);
 
+	/* FIXME: VTY code still uses NULL-context */
+	talloc_free(tall_vty_ctx);
+
 	/**
 	 * Report the heap state of NULL context, then free,
 	 * so both ASAN and Valgrind are happy...