Mute oscrc permissions warning when there's no password set

[dmach]

Fixes: #1677

[pep8speaks]

Hello @dmach! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file osc/conf.py:

Line 1909:121: E501 line too long (127 > 120 characters)

[johanneskastl]

I just copied the conf.py from this branch to /usr/lib/python3.11/site-packages/osc/conf.py and tried some osc commands.

I did not get a warning due to the wrong permissions on my oscrc, as intended by this change. So for me this seems to work.