Instead of just ignoring deployments with group:os-apply-config and
silently not applying them, this commit updates config-download to raise
an exception instead.
Deployments of this type are all deprecated across TripleO anyway,
although technically they may still work when not using config-download.
Raising an exception early will warn uses that they need to update any
custom deployments they may be using that still use
group:os-apply-config.
Change-Id: I2fb9ec3964b53d219905043a0cd9732aabbd88b2
Closes-Bug: #1741292
f32e264f7e