Use Android Q compatible external dir

We previously used Environment.getExternalDir to obtain the output dir for the tests. However, since Android Q this method is deprecated and returns an invalid path, leading to errors. Replace this method for context.getExternalDir(null) that return a Q  friendly path.

Test: atest FlickerLibTest
Bug: 161341377
Change-Id: I346074857478ba68d68fdbbf3b27bfcc98d79c0b
10 files changed
tree: f7e016af3370d4dc2dd11cba28561a3a6c02735f
  1. build/
  2. docs/
  3. emu_test/
  4. libraries/
  5. scripts/
  6. tests/
  7. utils/
  8. PREUPLOAD.cfg