Cleaning up resources on mount destruction.

DataLoaderStub's lifetime is controlled externally, but we want to
release resources ASAP.

Bug: b/153874006
Test: atest PackageManagerShellCommandTest PackageManagerShellCommandIncrementalTest IncrementalServiceTest
Change-Id: I34035f36d1fe4ed0e4916014d859feb7fe2c0a09
3 files changed