runit needs to record stderr and stdout.

If e.g. write outputs are failing, and collectd is trying to tell you about it, you will not see the error in the logs, only in the process table for runsvdir.  

This redirects stdout to stderr so svlogd records the failure.
From the man page for bash:
```
exec [-cl] [-a name] [command [arguments]]
    If command is specified, it replaces the shell. No new process is created. The arguments 
become the arguments to command. If the -l option is supplied, the shell places a dash at the 
beginning of the zeroth argument passed to command. This is what login(1) does. The -c option 
causes command to be executed with an empty environment. If -a is supplied, the shell passes 
name as the zeroth argument to the executed command. If command cannot be executed for 
some reason, a non-interactive shell exits, unless the shell option execfail is enabled, in which 
case it returns failure. An interactive shell returns failure if the file cannot be executed. If command 
is not specified, any redirections take effect in the current shell, and the return status is 0. If there 
is a redirection error, the return status is 1. 
```
Specifically: If command is not specified, any redirections take effect in the current shell, and the return status is 0.