Improve test coverage of ssh-keygen -T a bit. Upstream-Regress-ID: 8851668c721bcc2b400600cfc5a87644cc024e72
Add testcase for ssh-keygen -j, -J and -K options for moduli screening. Does not currently test generation as that is extremely slow. Upstream-Regress-ID: 9de6ce801377ed3ce0a63a1413f1cd5fd3c2d062