Fix default thread options for windows to not pin to any cpu_id (#1126)

Author: waahm7

source/windows/thread.c

@@ -21,6 +21,7 @@
 static struct aws_thread_options s_default_options = {
     /* zero will make sure whatever the default for that version of windows is used. */
     .stack_size = 0,
+    .cpu_id = -1,
     .join_strategy = AWS_TJS_MANUAL,
 };