cerebro_install_dir causes invalid permissions to be set

[Will Winder]

Using the default cerebro_install_dir=/opt causes invalid permissions to be applied to the directory. For my use case I was installing several services in /opt, but they fail because the permissions are restricted such that the services don't have access to the directory.

For a simple workaround, I found using cerebro_install_dir=/opt/cerebro fixes the problem.

[Matthew Plachter]

Thanks @winder I'll change the default Path