refactor(systemd): Drop unused unit_prefix feature

Fix #341
Merge pull request #342 from bcwaldon/341

Remove unit_prefix feature
fix(known-hosts): Use proper flag to build HostKeyFile
Merge pull request #344 from bcwaldon/fix-known-hosts

fix(known-hosts): Use proper flag to build HostKeyFile
Merge pull request #333 from jonboulle/master

Flag regression after refactor
refactor(fleetctl): Break apart lazyCreateJobs

The submit action needs to fail if it cannot create
a Job, while the other callers of lazyCreateJobs
just want to make sure a job/payload exist. Add a
test to solidify this behavior of fleetctl submit.
Merge pull request #348 from bcwaldon/fleetctl-behavior

refactor(fleetctl): Break apart lazyCreateJobs