Missing header meta_data.h

[Olivier Roques]

* Version of collectd: 5.9.2.g-1ubuntu5
* Operating system / distribution: Ubuntu 20.04
* Kernel version: 5.4.0-73-generic

I have developed a custom plugin for collectd that uses the plugin.h header. It worked fine on Ubuntu 18.04. But recently (May 2021) I've tried to recompile the plugin on Ubuntu 20.04 and it fails.

More specifically, this simple code does not compile anymore on Ubuntu 20.04 (I've installed the collectd, collectd-core, collectd-dbg, collectd-dev, collectd-utils packages but same error):

Code:
```
#include <collectd/core/daemon/plugin.h>

int main() {}
```

Output:
```
In file included from collectd.c:1:
/usr/include/collectd/core/daemon/plugin.h:34:10: fatal error: utils/metadata/meta_data.h: No such file or directory
   34 | #include "utils/metadata/meta_data.h"
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
```

meta_data.h is not present among the headers shipped with the collectd package on Ubuntu 20.04. Actually the whole utils folder is missing.

It seems this bug has been reported and fixed on Debian recently: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=968950

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.