use async delete when remove measures
use async delete when remove measures

we can async delete when remove metric measures because we remove
the xattr reference before so it shouldn't be queryable afterwards.

Change-Id: I9bfd45bb18af01c7f0579e832771a5a67d15ff67

leandroreox/gnocchi,leandroreox/gnocchi,gnocchixyz/gnocchi,sileht/gnocchi,sileht/gnocchi,gnocchixyz/gnocchi