Fix schema replication from old masters
    
    The new merged database will replicate with both the IPA and CA trees, so all
    DS instances (IPA and CA on the existing master, and the merged one on the
    replica) need to have the same schema.
    
    Dogtag does all its schema modifications online. Those are replicated normally.
    The basic IPA schema, however, is delivered in ldif files, which are not
    replicated. The files are not present on old CA DS instances. Any schema
    update that references objects in these files will fail.
    
    The whole 99user.ldif (i.e. changes introduced dynamically over LDAP) is
    replicated as a blob. If we updated the old master's CA schema dynamically
    during replica install, it would conflict with updates done during the
    installation: the one with the lower CSN would get lost.
    Dogtag's spawn script recently grew a new flag, 'pki_clone_replicate_schema'.
    Turning it off tells Dogtag to create its schema in the clone, where the IPA
    modifications are taking place, so that it is not overwritten by the IPA schema
    on replication.
    
    The patch solves the problems by:
    - In __spawn_instance, turning off the pki_clone_replicate_schema flag.
    - Providing a script to copy the IPA schema files to the CA DS instance.
      The script needs to be copied to old masters and run there.
    - At replica CA install, checking if the schema is updated, and failing if not.
      The --skip-schema-check option is added to ipa-{replica,ca}-install to
      override the check.
    
    All pre-3.1 CA servers in a domain will have to have the script run on them to
    avoid schema replication errors.
    
    https://fedorahosted.org/freeipa/ticket/3213