We don't have input devices in SDK thus for define/dumpxml
operations to be consistent we need to:

1. on dumpxml: infer input devices from other parts of config.
It is already done in prlsdkLoadDomain.

2. on define: check that input devices are the same that
will be infer back on dumpxml operation.

The second part should be fixed.
Signed-off-by: NNikolay Shirokovskiy <nshirokovskiy@virtuozzo.com>