Fix UserCache bug.

userSharesMediaWithParent() should not return 'true' for the user that
we run as, since that *is* the parent.

Bug: 189711032
Test: atest
android.appsecurity.cts.ExternalStorageHostTest#testMultiUserStorageIsolated

Change-Id: I78cb2e1f86cd58932759db28540c274bd13f2d34
1 file changed