fix: added correct checks to ssh public key checks

[cconstab]

This might well be better in an extension of String or function call but as this does not change often this will solve the short term issue and we can raise an issue to clean up later

- What I did
Identified that sshnpd also checks the public key validity, and hence the -s still fails to work and so addressed the issue
- How I did it
I added the same RegEx checks in two different places in the code
- How to verify it
Really needs to built so it can be tested as there is not yet a -s end to end test
- Description for the changelog

Fixed issue where the public keys was being tested incorrectly by sshnpd when using the -s flag on sshnpd and sshnp