Do storage checks before initiating a move.

Add new remote method to check for insufficient error conditions.
Some fixes in MountService when updating media status on PackageManagerService
Fix size calculation condition in installd.

Add new error code if media is unavailable.
New tests for testing error codes.
Some additional debugging statements in MountService.

Change-Id: Ibfe90d5ed6c71d57f9c1c67806f38b5ae9ecdfbf