commandserver: close service fds after fork

Summary:
After `fork()`, the chg worker no longer needs to detect incoming
connections using the selector, or `accept()` a connection. So let's just
close those fds explicitly.

Reviewed By: phillco

Differential Revision: D8384549

fbshipit-source-id: 9bd43692a575d425b61da8ad9c6b069113b2ae4b

mercurial/commandserver.py

@@ -526,6 +526,8 @@ class unixforkingservice(object):
                     conn.close()  # release handle in parent process
             else:
                 try:
+                    selector.close()
+                    self._sock.close()
                     self._runworker(conn)
                     conn.close()
                     os._exit(0)