efi_selftests: add extra testcases on controller handling

We recently fixed a few issues wrt to controller handling.  Add a few
test cases to cover the new code.
- return EFI_DEVICE_ERROR the first time the protocol interface of
  the controller is uninstalled, after all the children have been
  disconnected.  This should make the drivers reconnect
- add tests to verify controllers are reconnected when uninstalling a
  protocol fails
- add tests to make sure EFI_NOT_FOUND is returned if a non existent
  interface is being removed

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>