cec1ddc ipatests: fix modify_sssd_conf()

Authored and Committed by frenaud 4 years ago
    ipatests: fix modify_sssd_conf()
    
    The method modify_sssd_conf() is copying a remote sssd.conf file
    to the test controller then uses sssd python API to modify the
    config file.
    When the test controller does not have sssd-common package installed,
    SSSDConfig() call fails because the API needs sssd schema in order
    to properly parse the config file, and the schema files are provided
    by sssd-common pkg.
    The fix also downloads the files representing sssd schema and calls
    SSSDConfig() with those files. Using the schema from the test machine
    is ensuring that config is consistent with the schema (if the sssd
    version differs between controller and test machine for instance).
    
    Note: we currently don't see any issue in the nightly tests because
    the test controller is installed with sssd-common package but if you
    run the tests as specified in https://www.freeipa.org/page/Testing
    with a controller missing sssd-common, you will see the issue.
    
    Reviewed-By: Sergey Orlov <sorlov@redhat.com>