Merge branch 'ml/t9811-replace-test-f'

The test script 't/t9811-git-p4-label-import.sh' has been
modernized to use 'test_path_is_file' and 'test_path_is_missing'
instead of raw 'test -f' and '! test -f' calls.

* ml/t9811-replace-test-f:
  t9811: replace 'test -f' and '! test -f' with 'test_path_*'
  t9811: break long && chains into multiple lines