speed up ensuring correct file-permissions are set

[SvenRoederer]

During each container start the permissions for all relevant files are changed to have write-permission. For large data folders this will delay startup. Changing the permissions always also updates ctime of the file, which will trigger external backup solutions to include all files, even the content did not change.

This PR will check for incorrect permissions via "find" and only updated these files.

[SvenRoederer]

Runtime tested this as backport for my existing v4.1 instance. Difference to master is so small, that there is no other result to be expected.