Move javelin2 over to use oslo logging

javelin2 uses the tempest openstack clients which use oslo
logging, so make the logs generated directly by javelin2 and not the
tempest clients use oslo logging as well.

This way don't have to configure logging twice and can keep all javelin2
logs in the same place (as controlled by tempest.conf)

Change-Id: I09b5a13e9cd1511279163e07f780438c478d7af3
Merge "Move javelin2 over to use oslo logging"