Potential race condition when creating files

[pcuzner]

When we create files, and then chmod them there is a small window when the permissions are incorrect and exposed. We should therefore create the file with the correct permissions and avoid this 2 stage process.

An example of the fix required is here - https://git.centos.org/centos/centos-packager/c/ac981c91aed7f7a8579bd2608ce6b6681aeabc82