Cannot install on a VM

A user provided this error log to illustrate that they couldn't use the installer to install openvpn-admin on a VM.

```
gruntwork-install --binary-name openvpn-admin --repo https://github.com/gruntwork-io/terraform-aws-openvpn --tag v0.5.4
```

Error:
```
2021-07-02 12:08:08 [INFO] [gruntwork-install] Installing openvpn-admin...

2021-07-02 12:08:09 [INFO] [gruntwork-install] Moving /tmp/gruntwork-script-modules/openvpn-admin_linux_amd64 to /usr/local/bin/openvpn-admin and setting execute permissions

mv: cannot stat '/tmp/gruntwork-script-modules/openvpn-admin_linux_amd64': No such file or directory
```

We suspect that this has to do with the downloaded file being in the wrong place (i.e., the native system instead of the VM), or something like that. Is this a case we should support?

Workaround: Allow the script to complete and error out. Manually `scp` or otherwise locate the file and move it to the right place, adding execute permissions.

Start by reproducing the gruntwork-install command on a VM and tracing where the openvpn-admin_linux_amd64 download is placed before the move to /usr/local/bin. Compare the expected path with the actual downloaded file and verify that a successful installation leaves an executable openvpn-admin in the target location.

Written by the indexing model from the issue text.