We had previously weakened our nodeinfotest in order to ignore parsed
node values, because the parse function was mistakenly relying on
host files.  A better fix is to avoid using the numactl library, but
to instead parse the same files that numactl would read, all while
allowing the files to be relative to our choice of directory.

* src/nodeinfo.c (CPU_SYS_PATH, NODE_SYS_PATH): Replace with...
(SYSFS_SYSTEM_PATH): ...parent directory.
(linuxNodeInfoCPUPopulate): Check NUMA nodes from requested
directory (by inlining numactl code).
(nodeGetCPUmap, nodeGetMemoryStats): Adjust macro use.
* tests/nodeinfotest.c (linuxTestCompareFiles, linuxTestNodeInfo):
Update test to match.