Log active/pending/desired capacity (pending merge)

...on server active and server deleted and server failure.

This has several caveats.

1.  In audit logs, it really should be `active_capacity`, `pending_capacity`, and `desired_capacity` rather than `current_active`, `current_pending`, and `current_active`, BUT...
  -  in our API responses, the desired capacity is actually active+pending, so it might be weird for audit logs to not agree.  Granted, audit logs aren't out yet, so it doesn't matter, but if I name them `current_*`, our log filters will filter them out of the audit logs specifically (and not our non-audit logs)
  - the existing log for calculating delta names them this way.  I didn't want to break the dashboards

   The names *should* eventually be `active_capacity`, `pending_capacity`, and `desired_capacity`, just not sure if I should here or later.  @kivattik in particular.

2.  Note that under` _job_failed`, the logging changes slightly.  Tests pass, but is this change ok?