Fixes #5486: Use rotate instead of reload to trigger a rsyslog rotation ...

...in Rudder logrotate

Ticket: http://www.rudder-project.org/redmine/issues/5486

To be merged in 2.6
Ubuntu (until the next , unreleased versions) uses upstart, which states:
```
root@ubuntu-10-04-64:~# service rsyslog rotate
Rather than invoking init scripts through /etc/init.d, use the service(8)
utility, e.g. service rsyslog rotate

The script you are attempting to invoke has been converted to an Upstart
job, but rotate is not supported for Upstart jobs.
```

It seems on ubuntu, only reload is supported, so everything is OK.