We currently deny running scylla_setup when umask != 0022.
To remove this limitation, run os.chmod(0o644) on every file creation
to allow reading from scylla user.
Note that perftune.yaml is not really needed to set 0644 since perftune.py is
running in root user, but setting it to align permission with other files.
Fixes #8049
Closes #8119
(cherry picked from commit f3a82f4685)