Remove setaffinity of pthread for getaddrinfo

	It looks like `sched_getcpu(3)` returns a strange number on some
	(virtual?) environments.

	I decided to remove the setaffinity mechanism because the performance
	does not appear to degrade on a quick benchmark even if removed.

	[Bug #20172]
	---
	 ext/socket/extconf.rb  |  2 --
	 ext/socket/raddrinfo.c | 48 ++++--------------------------------------------
	 2 files changed, 4 insertions(+), 46 deletions(-)