Backporting the secondary user data dir fix.

It contains the minimal change for getting the AppDataDirGuesser to
correctly guess the data directory for a secondary android user.

Merged-In: Iddd7d3d71d3aa4cead1699d64481cff2f73abfbd

Fixes: 120550805
Test: atest CtsMockingTestCases
            CtsInlineMockingTestCases
            CtsMockingDebuggableTestCases

Change-Id: I7398acf5d526edb6ba7b68d1187bea038d0ae1bb