Fix 64-bit GraphicStats.findRootPath test

frameworks/base/libs/hwui/tests/unit/GraphicsStatsServiceTests.cpp:54: Failure
Value of: findRootPath()
  Actual: "/data/nativetest64/hwui_unit_tests"
Expected: expected
Which is: "/data/nativetest/hwui_unit_tests"
[  FAILED  ] GraphicsStats.findRootPath (1 ms)

Test: hwui_unit_tests
Change-Id: I809fcc9d5f640ecd4248a8ae2272c72ba4bd2cdd