all: Remove _ from simple for loops

Signed-off-by: Lewis Marshall <lewis@lmars.net>
Merge pull request #407 from flynn/gofmt-updates

gofmt: Remove _ from simple for loops
host: Exit containers on setup error

Signed-off-by: Lewis Marshall <lewis@lmars.net>
host: Ensure job errors are propagated via attach protocol

Signed-off-by: Lewis Marshall <lewis@lmars.net>