Fix booting from image instead of volume

NC-157, ITACLOUD-2840
Merge branch 'feature/itacloud-2840' into 'develop'

Fix provisioning from volume instead of image, ITACLOUD-2840
Use Django configured timezone for the beat
Fix merge conflicts markers, fix wording

ITACLOUD-2671
Merge branch 'feature/backup-merge-fix' into 'develop'

Fix merge conflict markers for backup refactoring branch

Some tests still fail, but at least they don't crash
Merge branch 'develop' of code.opennodecloud.com:nodeconductor/nodeconductor into develop
Fix default value calculation for usage stats
Make RelatedBackupField more resilient
Cleanup
Disable failing unittests