BUG/MEDIUM: lua: cannot process more Lua hooks after a "done()" function call

When the Lua execution flow endswith the command done (core.done or txn.done())
an error is detourned, and the stack is no longer usable. This patch juste
reinitilize the stack if this case is detected.

src/hlua.c

@@ -1000,6 +1000,7 @@ timeout_reached:
 		 */
 		if (lua->flags & HLUA_EXIT) {
 			ret = HLUA_E_OK;
+			hlua_ctx_renew(lua, 0);
 			break;
 		}