qemu: remove test for allowing ide controller in s390, rename usb tests
    
    Back in 2013, commit 877bc089 added in some tests that made sure no
    error was generated on a domain definition that had an automatically
    added usb controller if that domain didn't have a PCI bus to attach
    the usb controller to. This was done because, at that time, libvirt
    was automatically adding a usb controller to *any* domain definition
    that didn't have one.  Along with permitting the controller, two
    s390-specific tests were added to ensure this behavior was maintained
    - one with <controller type='usb' model='none'/> and another (called
    "s390-piix-controllers") that had both usb and ide controllers, but
    nothing attached to them.
    
    Then in February of this year, commit 09ab9dcc eliminated the annoying
    auto-adding of a usb device for s390 and s390x machines, stating:
    
     "Since s390 does not support usb the default creation of a usb
      controller for a domain should not occur."
    
    Although, as verified here, the s390 doesn't support usb, and usb
    controllers aren't currently added to s390 domain definitions
    automatically, there are likely still some domain definitions in the
    wild that have a usb controller (which was added *by libvirt*, not by
    the user), so we will keep the tests verifying that behavior for
    now. But this patch changes the names of the tests to reflect that
    they don't actually contain a valid s390 config; this way future
    developers won't propagate the incorrect idea that an s390 virtual
    machine can have a USB (or IDE) bus.
    
    In the case of the IDE controller, though, libvirt has never
    automatically added an IDE controller unless a user added an IDE disk
    (which itself would have caused an error), and we specifically *do*
    want to begin generating an error when someone tries to add an IDE
    controller to a domain that can't support one. For that reason, while
    renaming the sz390-piix-controllers patch, this patch removes the
    <controller type='ide'...> from it (otherwise the upcoming patch would
    break make check)