devserver.py: Move ExtractTarball to cros_build_lib.

BUG=chromium:925203, chromium:1141320
TEST=./devserver_integration_test.py

Cq-Depend: chromium:2501981, chromium:2489405
Change-Id: Ia1606e93dc4d31a1c6cec21f00a044879c8a9254
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2501981
Tested-by: Eliot Courtney <edcourtney@chromium.org>
Commit-Queue: Eliot Courtney <edcourtney@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
1 file changed