978466: fix missing socket info s390x/ppc64

Try to better handle system with no topology info

s390/ppc sometimes have pretty limited cpu topology
info available, especially on rhel5. Try to handle
those cases.

On s390x systems, that have a "cpu topology" info in
/proc/sysinfo and populated
/sys/devivces/system/cpu/cpu*/topology, we defer to
the latter. This is the scenario for s390x on zvm
running RHEL6.

Systems running RHEL5 will not have the /sys info
populated, so fall back to the /proc/sysinfo in
those cases.

For RHEL5 ppc64 systems with no /sys cpu topology
exposed, attempt to check cpu/cpuN/physical_id
for topology info.

If that doesn't have useful info, fallback
to 1 thread = 1 cpu = 1 core = 1 socket

Added cpu_t.topology_source fact to track how
client determined cpu topology info.