Added clearing of cpu_affinity after process spawn. This fixes unwanted/incorrect cpu_affinity use on dead worker processes respawn. While this is not ideal, it's expected to be better when previous situation where multiple processes were spawn with identical CPU affinity set. Reported by Charles Chen.

--- a/src/os/unix/ngx_process_cycle.c
+++ b/src/os/unix/ngx_process_cycle.c
@@ -371,6 +371,8 @@ ngx_start_worker_processes(ngx_cycle_t *
 
         ngx_pass_open_channel(cycle, &ch);
     }
+
+    cpu_affinity = 0;
 }