HDDS-2658. Insight log level reset does not work

[adoroszlai]

What changes were proposed in this pull request?

Reset log level to INFO in a shutdown hook instead of finally block.

https://issues.apache.org/jira/browse/HDDS-2658

How was this patch tested?

Tested on compose cluster:

# terminal 1
cd hadoop-ozone/dist/target/ozone-0.5.0-SNAPSHOT/compose/ozone
docker-compose up -d
docker-compose logs -f om

# terminal 2
cd hadoop-ozone/dist/target/ozone-0.5.0-SNAPSHOT/compose/ozone
docker-compose exec om bash
ozone insight logs -v om.protocol.client

# terminal 3
cd hadoop-ozone/dist/target/ozone-0.5.0-SNAPSHOT/compose/ozone
docker-compose exec om ozone freon ockg -F ONE -n 1

Verified that ozone insight shows trace-level log. Stopped ozone insight on terminal 2 (Ctrl-C). Verified that creating another volume is logged in terminal 1 (ie. OM), but debug/trace-level messages are not:

# terminal 3
$ docker-compose exec om ozone freon ockg -F ONE -n 1 -v vol2

# terminal 1
om_1        | 2019-12-03 11:49:49,114 INFO volume.OMVolumeCreateRequest: created volume:vol2 for user:hadoop

https://github.com/adoroszlai/hadoop-ozone/runs/330882658

[adoroszlai]

Thanks @elek for committing this.