server upgrade: always upgrade KRA agent PEM file
    
    Before the KRA agent PEM file is exported in server upgrade, the sysupgrade
    state file is consulted. This causes the KRA agent PEM file not to be
    exported to the new location if the upgrade was executed in the past.
    
    Do not consult the sysupgrade state file to decide whether to upgrade the
    KRA agent PEM file or not, the existence of the file is enough to make this
    decision.
    
    https://fedorahosted.org/freeipa/ticket/6675
    
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>