microceph log set-level doesn't change loglevel

# Issue report

## What version of MicroCeph are you using ?

microceph (edge) 19.2.0~git+snapc76c1f5fe9 from Canonical✓ installed

## What are the steps to reproduce this issue ?

```
sudo snap install microceph --channel latest/edge
microceph (edge) 19.2.0~git+snapc76c1f5fe9 from Canonical✓ installed
sudo microceph cluster bootstrap
sudo microceph log set-level 5
sudo microceph disk add loop,2G,3

+-----------+---------+
| PATH | STATUS |
+-----------+---------+
| loop,2G,3 | Success |
+-----------+---------+
fgrep -c "Adding OSD" /var/log/syslog
0
```

## What happens (observed behaviour) ?

Some expected log messages such as the Debugf("Adding OSD...") are not present in /var/log/syslog

## What were you expecting to happen ?

After setting level 5 (DEBUG) I'd expect debug log messages to appear

## Additional comments.

In issue #339 an issue is listed resetting log level after microcephd restarts -- but now it seems set-level doesn't do anything