config.scm (config-save-list): Fix a bug.

* lazycat-daemon/config.scm (config-save-list): Fix a bug: use
  call-with-output-file instead of with-output-to-file.  The problem
  with with-output-to-file is that the daemon closes all the default
  ports including stdout on start, but call-with-output-file seems
  to fail because it tries to restore the default output port after
  a thunk is done.  It means that the lazycat-daemon fails when it
  tries to save the host list to a file -- and we can't stop proxy
  processes.  What an annoying bug.