[libvirt] UML driver struct refers to public API functions

[Matthias Bolte]

Hi,

The commit "Generic shared impls of all NUMA apis"
(b0b968efd56f6c66bfa23eebbecd491ea993f99b) changed the UML driver
struct to use the shared NUMA API. But now the UML driver struct
refers to the public API functions:

virNodeGetCellsFreeMemory
virNodeGetFreeMemory

instead of the shared NUMA API functions

nodeGetCellsFreeMemory
nodeGetFreeMemory

This results in an infinite recursion, if someone's going to call
virNodeGetCellsFreeMemory with an UML connection.

Matthias