Code review comment for lp:~wallyworld/juju-core/agent-conf-upgradedto

Reviewers: mp+207600_code.launchpad.net,

Message:
Please take a look.

Description:
Record upgradedToVersion in agent conf

The agent config files now record the version for
which upgrade steps were run. If there is no entry
in a config file, is is assumed the version is 1.16.
So there is no need for any migration, nor are there
compatibility issues. When 1.18 is deployed, the upgrade
steps are run and the config file will have 1.18 written
to it, allowing 1.20 to know that it is upgrding from
1.18 etc.

https://code.launchpad.net/~wallyworld/juju-core/agent-conf-upgradedto/+merge/207600

(do not edit description out of merge proposal)

Please review this at https://codereview.appspot.com/66870044/

Affected files (+332, -203 lines):
   A [revision details]
   M agent/agent.go
   M agent/agent_test.go
   M agent/bootstrap_test.go
   M agent/format-1.12_whitebox_test.go
   M agent/format-1.16.go
   M agent/format-1.16_whitebox_test.go
   M agent/format_whitebox_test.go
   M cmd/jujud/agent_test.go
   M cmd/jujud/bootstrap_test.go
   M environs/cloudinit/cloudinit.go
   M juju/testing/conn.go
   M worker/deployer/simple.go
   M worker/provisioner/kvm-broker_test.go
   M worker/provisioner/lxc-broker_test.go