ipatests: call server-del before replica uninstall
    
    The test test_replica_promotion.py::TestRenewalMaster::
    test_automatic_renewal_master_transfer_ondelete is calling
    ipa-server-install --uninstall directly without performing first
    ipa server-del. This can lead to incomplete uninstallation and
    test failures.
    Call tasks.uninstall_replica instead of tasks.uninstall_master.
    This is equivalent to ipa-replica-manage del + uninstall
    (ipa-replica-manage del works in DL0 and DL1 and internally calls
    ipa server-del in DL1).
    
    Fixes: https://pagure.io/freeipa/issue/8792
    Signed-off-by: Florence Blanc-Renaud <flo@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>