Only add certificates for authenticated users and only add root

Only add certificates for authenticated users and only add root
certificate if running as root...

scheduler/cert.c:
    - InitCerts(): Only add root certificate when running as root.

scheduler/client.c:
    - pipe_command(): Only add certificate for authenticated users.

scheduler/main.c:
    - main(): Only add root certificate when running as root.
    - select_timeout(): Only schedule time for root cert update when running as root.

git-svn-id: svn+ssh://src.apple.com/svn/cups/cups.org/trunk@4629 7a7537e8-13f0-0310-91df-b6672ffda945