Follow storage API polishing.

Test: cts-tradefed run commandAndExit cts-dev -m CtsAppSecurityHostTestCases -t android.appsecurity.cts.StorageHostTest
Bug: 37325923, 35812899, 35806020
Change-Id: I4965b7391018354157f0683a643a14c5e9cd338d
7 files changed