Remove unused var (ws_) and use vars in undefined case for compile (#20667)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20667
Compilation errors:
```
xplat/caffe2/caffe2/utils/signal_handler.h:31:10: error: private field 'SIGINT_action_' is not used [-Werror,-Wunused-private-field]
Action SIGINT_action_;
^
xplat/caffe2/caffe2/utils/signal_handler.h:32:10: error: private field 'SIGHUP_action_' is not used [-Werror,-Wunused-private-field]
Action SIGHUP_action_;
^
xplat/caffe2/caffe2/utils/signal_handler.h:33:17: error: private field 'my_sigint_count_' is not used [-Werror,-Wunused-private-field]
unsigned long my_sigint_count_;
^
xplat/caffe2/caffe2/utils/signal_handler.h:34:17: error: private field 'my_sighup_count_' is not used [-Werror,-Wunused-private-field]
unsigned long my_sighup_count_;
^
4 errors generated.
xplat/caffe2/caffe2/share/fb/stylizer/median_blur_ops.cc:593:14: error: private field 'ws_' is not used [-Werror,-Wunused-private-field]
Workspace* ws_;
^
1 error generated.
```
Reviewed By: bwasti
Differential Revision: D15402928
fbshipit-source-id: 5b98499850aa659fd37ab8e7f2e75166787b8129
