baseimage: workaround for zsh package installation error

error detail:

```
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
zsh : Depends: zsh-common (= 5.0.7-3+b1) but 5.0.7-3 is to be installed
E: Unable to correct problems, you have held broken packages.
```

zsh, zsh-common package versions (`apt-cache policy zsh zsh-common`):

```
zsh:
  Installed: (none)
  Candidate: 5.0.7-3+b1
  Version table:
     5.0.7-3+b1 0
        500 http://ftp.jp.debian.org/debian/ sid/main amd64 Packages
zsh-common:
  Installed: (none)
  Candidate: 5.0.7-3
  Version table:
     5.0.7-3 0
        500 http://ftp.jp.debian.org/debian/ sid/main amd64 Packages
```