Cells: Add cells support to instance_usage_audit_log api extension

Adds task_log_get_all() call to HostAPI() so that we can use the local
DB when cells is disabled or proxy via cells if cells is enabled.

Adds task_log_get_all() call to cells.

Change-Id: I9e78c17fcf70f98903d0a26c1de3e2581b8977ad
Merge "Cells: Add cells support to instance_usage_audit_log api extension"