Reduce the number of hazard pointers

Reduce the number of hazard pointers

Previously, we set the number of the hazard pointers to be 4 times the
number of workers because the dispatch ran on the old socket code.
Since the old socket code was removed there's a smaller number of
threads, namely:

 - 1 main thread
 - 1 timer thread
 - <n> netmgr threads
 - <n> threadpool threads

Set the number of hazard pointers to 2 + 2 * workers.