Remove dependency on internal FileUtils class

In preparation for building android.legacy.test library against
the test API this removes a dependency on internal classes.

Bug: 30188076
Test: make checkbuild cts-tradefed run cts -m CtsContentTestCases -t android.content.cts.SyncStorageEngineTest
Change-Id: I4c0e7fdd368e96459c8404ff7cea8738683d0ec1
1 file changed