Enable dalvik.system.BlockGuardTest#testFileInputStream test

As /proc/version is no longer accessible to CTS tests, the test now
creates and uses a temporary file instead.

Bug: 29495646
Test: cts-tradefed run cts -m CtsLibcoreTestCases -t \
      dalvik.system.BlockGuardTest#testFileInputStream

Change-Id: I1cc4b89f885e906218f5a706cd8cbbeedde70393
2 files changed