Ignore exception when unlink /tmp/autotest_results_dir.* failed

Sometime when users execute a test, at the end, there's a error happened ,such as :
```
07:46:42 DEBUG|   File "/github-autotest_new/client/test.py", line 95, in crash_handler_report
07:46:42 DEBUG|     os.unlink(self.debugdir_tmp_file)
07:46:42 DEBUG| OSError: [Errno 2] No such file or directory: '/tmp/autotest_results_dir.8971'
```
I don't know what caused this error yet, when execute test second time, maybe this won't happen.
I think this error should be ignored , then test can run successfully