ART: Remove test files after test

The unix_file tests should remove files and directories when they
are done testing.

Bug: 16505797

(cherry picked from commit 7747c8de402f64e3009ca3bcccebddbb70f617ee)

Change-Id: I9c3c8f1a80ec0d37628a742193267e182c25b0cd
6 files changed