Increase memory usage for Azure CI upgrade test
    
    The test often fails when running in parallel to other tests as very
    little memory is left. 389-ds memory autotuning causes database backend
    to refuse working in such cases. 389-ds team suggested more memory has
    to be made available.
    
    Increate RAM for this test to 2.5GB instead of 2.2GB.
    
    Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>