Refactor sysconf checking
The introduction of layered checking for hardware topology left
checking based on sysconf and OpenMP applying in cases where it is
unclear whether the conclusions are valid, and surely difficult to
test reliably.
Instead, those checks should apply only to sysconf-based detection
(which is the final fallback case). Those are refactored here with a
view to code changes that will merge shortly from release-5-1.
Removed a one-line output to the debug stream.
Change-Id: Ide56fa8d6817608fba9f29a05da10034ae543b75