Avoid double-quoting of group names for yum

This PR fixes usage of trying to use the module ``pkg.group_install`` with quoted group names on RPM-based distros.  Trying to install ``Development tools``, for instance, results in commands being issued like this:

```
[INFO    ] Executing command 'repoquery --plugins --group --info "\'Development tools\'"' in directory '/root'
```

which fails, because ``'Development tools'`` doesn't exist (the single quotes are taken into account as they're within the double quotes).

The command templates are adjusted in this PR to avoid double-quoting.  The incoming group ``name`` is already quoted by ``_cmd_quote`` in both of this situations, so using repr string formatting isn't necessary.