ipa-server-install: Remove the --selfsign option
    
    Instead, certificates in pkcs12 files can be given to set up
    IPA with no CA at all.
    Use a flag, setup_ca, to signal if a CA is being installed.
    
    Design: http://freeipa.org/page/V3/Drop_selfsign
    Part of the work for: https://fedorahosted.org/freeipa/ticket/3494