Add notify_inval_inode and extend get_rootfs to return fs_idx for umount#211

imeoer merged 1 commit intocloud-hypervisor:mastercloud-hypervisor/fuse-backend-rs:masterfrom

sidneychang:notify-inval-inode-and-get-rootfs-fsidxsidneychang/fuse-backend-rs:notify-inval-inode-and-get-rootfs-fsidxCopy head branch name to clipboard