vtysh: fix a memory leak in vtysh_client_execute

buf is dynamically allocated and needs to be freed in the error handling
path too.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Acked-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/vtysh/vtysh.c b/vtysh/vtysh.c
index 23653f0..d0cc2eb 100644
--- a/vtysh/vtysh.c
+++ b/vtysh/vtysh.c
@@ -137,6 +137,7 @@
 	{
 	  fprintf (stderr, ERR_WHERE_STRING \
 		   "warning - pbuf beyond buffer end.\n");
+	  XFREE(MTYPE_TMP, buf);
 	  return CMD_WARNING;
 	}