xacro: 1.8.6-0 in 'hydro/distribution.yaml' [bloom]

Increasing version of package(s) in repository `xacro` to `1.8.6-0`:

- distro file: `hydro/distribution.yaml`
- bloom version: `0.5.10`
- previous version for package: `1.8.5-0`

## xacro

```
* fix tests file so they run properly
* Contributors: Michael Ferguson
```