Unit state during charm upgrade

[Francesco Banconi]

Hi everybody,

while working on functional tests for our charms, I've seen that, having
a started unit, the unit state remains "started" during charm upgrade.

In my tests I ended up waiting a few seconds before checking the unit
state using `juju status`. However, in my opinion, the charm upgrade
could be more testable if a state transition is performed during upgrade.
E.g.: the charm switch to state "pending" (or "upgrading" or something
else) when `juju upgrade-charm` is invoked, and then back again to
"started" if the hook completes successfully.

I hope my suggestion will be of some use.
Thank you!

-- 
Francesco Banconi