Update logrotate.

Without this change, logrotate complains:

error: skipping "/var/log/karaage/django.log" because parent directory
has insecure permissions (It's world writable or writable by group which
is not "root") Set "su" directive in config file to tell logrotate which
user/group should be used for rotation.

Change-Id: I7cff04564f12c029889a1fd38eda03dc374a7e51