registry: update job when migrating legacy payload
systemd: log length of unit being written
agent: use correct Job object in LoadJob task

Fix #737
Merge pull request #738 from bcwaldon/737

Carry actual unit file into Agent LoadJob task
etcd: refactor TLS configuration

Separate reading files from creating a TLS config object.
Merge pull request #734 from bcwaldon/migrate-payload-job

registry: update job when migrating legacy payload
Merge pull request #731 from bcwaldon/refactor-etcd-tls

etcd: refactor TLS configuration
engine: tweak lease logging
engine: limit reconciliation duration

A reconciliation attempt should stop when the lease is no longer
held by a given agent to prevent conflict with other engines.
engine: make reconcile interval configurable