[test_utils] Do not re-download ATNT database

if the data is already inside the low-level db package.
Fixes #127
4 jobs for use-default-atnt-directory in 7 minutes and 54 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Build
passed #218948
docker
build_linux_37

00:07:54

84.0%
passed #218947
macosx
build_macosx_37

00:06:12

84.0%
failed #218908
docker
build_linux_37

00:05:13

83.0%
failed #218907
macosx
build_macosx_37

00:04:34

83.0%