Fix deploy loop bug when evaluation didnt include a deployment ID.
Fix deploy loop bug when evaluation didnt include a deployment ID.

In situations where the deployed evaluations didn't invoke a
deployment, the return from the Nomad eval endpoint would include
an empty deployment ID. Levant would continue to retry until the
deployment ID object was populated, which possibly wouldn't
happen causing Levant to get stuck in a loop forever.

This change adds a timeout into the function which performs the
above work, so that if after 60s no deployment ID has been
returned, Levant will exit with a useful message.

Closes #263

jrasell/levant