Issues with non-zero exit codes on timeouts

[emperorcow]

Getting an error with non-zero exit codes on a script when they timeout.

`panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0xc40a00]

goroutine 21578 [running]:
github.com/gen0cide/laforge/core.(*Connection).ExecuteString.func4(0xc002606fc0)
/home/emperorcow/go/src/github.com/gen0cide/laforge/core/connection.go:326 +0x8d0
created by github.com/gen0cide/laforge/core.PerformInTimeout
/home/emperorcow/go/src/github.com/gen0cide/laforge/core/generic_job.go:125 +0x140
`