Prevent 'Could not change permissions' warnings with CiviCRM

I was getting messages like `"Could not change permissions <...>/files/civicrm/templates_c to 2770 (chmod to 2770 failed on <...>/files/civicrm/templates_c)` when verifying sites with CiviCRM installed. I'd like the nice green status back :)

Similar to [this previous issue](https://www.drupal.org/node/1920972).

Untested but this should work. Note there's also a `civicrm/ConfigAndLog` folder, but I'm not getting warnings for that one. Should it also be changed?