Audit bootstrap to fix jq error

[troglobit]

On first boot, no startup-config, the bootstrap script logs this slightly worrying line:

Jan 21 21:17:18 infix finit[1]: Starting bootstrap[780]
Jan 21 21:17:18 infix bootstrap[780]: jq: error (at <stdin>:0): Cannot iterate over null (null)

Probably missing a file exists check.