* Expose the authorized keys tmate feature
Described here: https://tmate.io/ in "Access Control"
The variable accepts the file content in raw format (with \n) and dumps it into a file which tmate reads
* Use echo instead of printf
* Add missing quote
* Only setup tmate settings if debug is activated
netrc gem checks for permissions and drone-runner-docker creates the file with 644 permission
```
Netrc::Error:
Permission bits for '/root/.netrc' should be 0600, but are 644
```
