man: can't open /usr/share/man/man8/init.8: No such file or directory

[Alexander Pozdneev]

I run Ubuntu 16.04.5 LTS and the value of `LANG` is `en_US.UTF-8`.

After quitting the `man upstart` page I see the following message in terminal:
```
man: can't open /usr/share/man/man8/init.8: No such file or directory
```
And `locate init.8` confirms that there is no such file.

The `apt-file find init.8` command shows that `init.8.gz` is present in `manpages-es-extra`, `manpages-hu` and similar packages for other languages (but not for English).

This is the output of `gunzip -c /usr/share/man/man7/upstart.7.gz`:
```
.so man8/init.8
```
(So, it looks like this is an incorrect redirection.)

I believe, `upstart.7.gz` should be fixed.

Information about release and package version:

$ lsb_release -rd
Description: Ubuntu 16.04.5 LTS
Release: 16.04

$ apt-cache policy upstart
upstart:
  Installed: 1.13.2-0ubuntu21.1
  Candidate: 1.13.2-0ubuntu21.1
  Version table:
 *** 1.13.2-0ubuntu21.1 500
        500 http://ru.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1.13.2-0ubuntu21 500
        500 http://ru.archive.ubuntu.com/ubuntu xenial/main amd64 Packages

This might be a related bug: https://bugs.launchpad.net/ubuntu/+source/manpages/+bug/252413