Perform a number of new checks to assess the status of the
local unit:
- Presence and completeness of relations
- Status of vault (initialized, sealed)
- Configuration of memory locking
This review also switches a number of 'status_set' calls to
be 'log' calls to avoid continually polluting the Juju status
display with non-pertinent information during update-status
executions.
Change-Id: I4e467a76bb0951deda8a88c609f4c79f4b0b33f4
68068c64d8