Zero the tdb key, there might be padding

This leads to uninitialized variable warnings if nmbd is run under valgrind.

source/libsmb/unexpected.c

@@ -63,6 +63,8 @@ void unexpected_packet(struct packet_struct *p)
 
 	len = build_packet(&buf[6], sizeof(buf)-6, p) + 6;
 
+	ZERO_STRUCT(key);	/* needed for potential alignment */
+
 	key.packet_type = p->packet_type;
 	key.timestamp = p->timestamp;
 	key.count = count++;