systemtest: regenerate host credentials, add user credentials

Patch adds new host credentials so the system-test continues to work
out-of-the-box.  The patch also adds user-certificates generated by
the same Disposable CA.  This should allow people without an X.509
certificate to use system-test without first regenerating credentials.

Target: master
Request: 2.9
Request: 2.8
Request: 2.7
Request: 2.6