process_lxd_resources converts numa_nodes dictionary to a list

While testing the NodeDevices code in the CI I ran into a failure on our PPC64 machine. When I investigated I noticed that NUMA nodes are configured as 0, 1, 16, 17. _process_lxd_resources processes the numa nodes as a dictionary but converts them into a list. update_node_network_information, update_node_physical_block_devices, and now update_node_devices process hardware and read the numa_node number from LXD and then access it by indexing numa_nodes. This only works when there are no gaps in the sequence. Keep numa_nodes as a dictionary fixes the issue.

This wasn't caught before because all network cards are on numa_node 1. Only PCIE bridges are used on numa_node 16 and 17.