Xubuntu の lsb_release に 17.04 Zesty Zapus (開発ブランチ) が表示されています

Question

1 か月前に Xubuntu 16.10 をインストールしました。現在、私のシステムでは 17.04 (開発ブランチ) を実行していることが表示されます。

$ lsb_release -a

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu Zesty Zapus (development branch)
Release:    17.04
Codename:   zesty

システムを最新のプレリリース バージョンにアップグレードすることを許可していなかったと思います。Ubuntu のソフトウェアとアップデートも開きません。こちら:

$ software-properties-gtk
aptsources.distro.NoDistroTemplateException: Error: could not find a distribution template for Ubuntu/zesty

システムのsources.listには、パッケージが以下からインストールされていることが示されています。ヤッケティリポジトリ。

# deb cdrom:[Xubuntu 16.10 _Yakkety Yak_ - Release amd64 (20161012.2)]/ yakkety main multiverse restricted universe

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://in.archive.ubuntu.com/ubuntu/ yakkety main restricted
# deb-src http://in.archive.ubuntu.com/ubuntu/ yakkety main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://in.archive.ubuntu.com/ubuntu/ yakkety-updates main restricted
# deb-src http://in.archive.ubuntu.com/ubuntu/ yakkety-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://in.archive.ubuntu.com/ubuntu/ yakkety universe
# deb-src http://in.archive.ubuntu.com/ubuntu/ yakkety universe
deb http://in.archive.ubuntu.com/ubuntu/ yakkety-updates universe
# deb-src http://in.archive.ubuntu.com/ubuntu/ yakkety-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://in.archive.ubuntu.com/ubuntu/ yakkety multiverse
# deb-src http://in.archive.ubuntu.com/ubuntu/ yakkety multiverse
deb http://in.archive.ubuntu.com/ubuntu/ yakkety-updates multiverse
# deb-src http://in.archive.ubuntu.com/ubuntu/ yakkety-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://in.archive.ubuntu.com/ubuntu/ yakkety-backports main restricted universe multiverse
# deb-src http://in.archive.ubuntu.com/ubuntu/ yakkety-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu yakkety partner
# deb-src http://archive.canonical.com/ubuntu yakkety partner

deb http://security.ubuntu.com/ubuntu yakkety-security main restricted
# deb-src http://security.ubuntu.com/ubuntu yakkety-security main restricted
deb http://security.ubuntu.com/ubuntu yakkety-security universe
# deb-src http://security.ubuntu.com/ubuntu yakkety-security universe
deb http://security.ubuntu.com/ubuntu yakkety-security multiverse
# deb-src http://security.ubuntu.com/ubuntu yakkety-security multiverse

これを解決するのを手伝ってくれる人はいますか? 16.10 をインストールしたのに、なぜシステムに 17.04 が表示されるのかわかりません。

参照 私のコンピューターはUbuntu 17.04を実行していると表示されています、以下は出力です

apt-cache policy base-files:

base-files:
  Installed: 9.6ubuntu6
  Candidate: 9.6ubuntu6
  Version table:
 *** 9.6ubuntu6 500
        500 http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu yakkety/main amd64 Packages
        100 /var/lib/dpkg/status
     9.6ubuntu5 500
        500 http://in.archive.ubuntu.com/ubuntu yakkety/main amd64 Packages