Removed call to iocp_initialize_winsock in IOCP plugin.

This is already called directly from the core

Change-Id: I1a0c5651a0763318e7032c9275d83a2d5ccd01c2
Reviewed-on: http://review.couchbase.org/29756
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>