check_log.sh: [ShellCheck](http://www.shellcheck.net/) fails (#1366)

[Elan Ruusamäe]

use backticks to quote output in ticket:

    ```
    foo
    ```

-- 
Reply to this email on GitHub:
https://github.com/monitoring-plugins/monitoring-plugins/issues/1366#issuecomment-145488027
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://www.monitoring-plugins.org/archive/devel/attachments/20151005/90508a3c/attachment.html>