Disable setting the thread affinity (v9.16)

It was discovered that setting the thread affinity on both the netmgr and netthread threads lead to inconsistent recursive performance because sometimes the netmgr and netthread threads would compete over single resource and sometimes not.

Removing setting the affinity causes a slight dip in the authoritative performance around 5% (the measured range was from 3.8% to 7.8%), but the recursive performance is now consistently good.

(cherry picked from commit a9e6a7ae)

Closes #2822 (closed)