Move AD trust installation code to a separate module
    
    This facilitates calling the necessary checks and configuration code as
    a module from e.g. a composite installer. The code that checks for the
    admin credentials stays in the standalone installer as the code inside
    the adtrust module is expected to operate also without admin
    credentials.
    
    https://fedorahosted.org/freeipa/ticket/6629
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>