Support deconfiguring log archiving in Db2 instances

[fketelaars]

Is your feature request related to a problem? Please describe.
Db2 instances used for demos do not require archive logging. It should be possible to switch it off.

Configuration:

- name: db2
    description: Db2 OLTP
    size: small
    instances:
    - name: datastore
      metadata_size_gb: 20
      data_size_gb: 20
      backup_size_gb: 20  
      transactionlog_size_gb: 20
    state: installed

Add parameter log_archiving (True/False) to the instance settings.

Change in the config map

"*-db2dbconfig" and change line:
LOGARCHMETH1 DISK:/mnt/logs/archive
to:
LOGARCHMETH1 OFF