gce: do not use deprecated string.split func

We use the modern split function that's built into all strings.

BUG=None
TEST=`./cbuildbot/run_tests` passes

Change-Id: I1ec831ad6433c82047e656af8128e814df99f987
Reviewed-on: https://chromium-review.googlesource.com/319430
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Daniel Wang <wonderfly@google.com>
1 file changed