Force the CPU affinity for ru_thread explicitly to ru_thread_core. It is
already done via threadCreate(), but force again as per change request.

Delete commented 7.2 code that did the equivalent. We cannot set it in
the driver, as we don't have access to variable ru->ru_thread_core.

Closes: #732 (suggestion 2)
Suggested-by: Andrew Sergeev <andrew.sergeev@adtran.com>