fix(initialize): ensure update-engine is restarted after group/server
changes
Merge pull request #141 from jonboulle/141

cloudinit doesn't restart update-engine.service
fix(system): write all files atomically
fix(system): use workspace for temporary files in WriteFile
fix(system): rework WriteFile to take a relative path
fix(system): ensure tempfile is on same filesystem
fix(system): chmod before rename
fix(system): chown before rename