nodeinfo: Don't fail on non-contiguous NUMA topologies

nodeinfo: Don't fail on non-contiguous NUMA topologies

nodeGetFreeMemory and nodeGetCellsFreeMemory assumed that the NUMA nodes
are contiguous and starting from 0. Unfortunately there are machines
that don't match this assumption:

available: 1 nodes (1)
node 1 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
node 1 size: 16340 MB
node 1 free: 11065 MB

Before this patch:
error: internal error Failed to query NUMA free memory
error: internal error Failed to query NUMA free memory for node: 0

After this patch:
Total: 15772580 KiB
0: 0 KiB

Signed-off-by: Peter Krempa <pkrempa@redhat.com>