Fix file permission issue

The ticket link is:

https://arraynetworks.atlassian.net/browse/TWSD-1095
We should add cookie log by PHP.

However,

There is no permission for PHP to create file under the directory /var/log/.

So I modified the shell script to create file /var/log/aproxy_cookie.log if there is not exists.

Besides,

I changed the owner to nobody for the user of lighttpd is nobody.

Then changed the permission to 664 as (rw-rw-r--)

After that, PHP can edite the file successfully.