Beware 2.2.7 release

[Tim Penhey]

Hi folks,

Last night we were alerted to a fundamental issue with the 2.2.7 agent
only release.

There was a weird race condition that was only observable on larger
models which would cause a model to be non-responsive to controller
generated events, like config updates, actions, juju run etc.

We have a fix available, and it has been tested on one of the broken
controllers and shown to fix the problem.

Expect a 2.2.8 agent only release shortly to address this issue.

Thanks
Tim