Failed deployment DownloadBundle events with error "No such file or directory - getcwd"

Deployment failed during Download bundle event : with unknown error "No such file or directory - getcwd"

It's not a duplicate issue of #255, the error is different.

Our production server encountered this issue today.

```
$ sudo lsof -p 650
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
ruby 650 root cwd DIR 259,3 6 205521082 /opt/codedeploy-agent/deployment-root/bc3648ae-4408-4e76-9ff2-66603cd21741/d-0G43URW03/deployment-archive (deleted)
ruby 650 root rtd DIR 259,3 257 96 /
ruby 650 root txt REG 259,3 68480 13134719 /usr/bin/ruby
```

If we check the `codedeploy-agent` with `lsof`, we can find the `cwd` has changed to the directory of a past deployment which has been deleted. This deployment was created 3 days ago.

Version: 1.6.0-49

Restarting the codedeploy service resolved the problem.