Clear new or building backups on reset-task-status

The reset-task-status management call now also clears off
any new or building backups for the instance by marking
those backups as FAILED.

Fixes Bug # 1205471

Change-Id: I478782b5e90c9965b91169a784b2ea65bda8a8b4
Merge "Clear new or building backups on reset-task-status"