fix unterminated quoted string

I was able to reproduce error even w/o my previous changes this part always fails. Only reason it won't detected because it was never run, all installations was completed normally.

I only tested it with fail scenario (run stand-alone install.sh on ONIE), didn't have time to build ONL images
Also I'm not sure why we need say twice "Installer failed.", but keep it for sake of simplicity fix. I'd propose something like that
```
trap 'cat /var/log/onie.log > /dev/console; installer_say "Install failed. See log messages above for details"; sleep 3; reboot' EXIT
```