Refactor quota ops to a separate utils

Bug: 110380029
Test: - android.appsecurity.cts.StorageHostTest - all passes either when
running in bulk or when running alone (some tests somehow fails when
running in bulk - but passes when running alone. This also happens
before this CL, so the failure is not caused by this CL).
- Also tested with quota disabled.

Change-Id: I7a950115153378c9aeda86dd46bfa10f67c4e464