The charm currently does not report any workload status. This change
adds support for this.
Change-Id: I2586307c7beec5dc518a7b51c0737cca6105059d
Closes-Bug: 1604580
All contributions to this charm where made under Canonical
copyright; switch to Apache-2.0 license as agreed so we
can move forward with official project status.
Change-Id: I57efcf92ebd630190d351e8203c409d9c3136211