Flicker: Change default test artifact location

Changing default test artifact location to a new directory to make it easier to
capture with TF.

Bug: 64532606
Test: atest FlickerTests
forrest test th:cl:4468718:taimen-userdebug:git_master atp:/google/src/cloud/vishnun/flicker_gcl/google3/wireless/android/test_tools/atp/config/test/apct/instr_test-large-flicker.gcl

Change-Id: If718fc03918a1efba9a1f8a11cce3033397ba7f2