cros: extract repeating steps from EnrollmentScreenTest

Into Setup/Teardown functions

TBR=jdufault@chromium.org

Bug: 912704
Change-Id: Iacc83b65a831589dc7206489cf8b7723d3af4e1a
Reviewed-on: https://chromium-review.googlesource.com/c/1472574
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Reviewed-by: Denis Kuznetsov <antrim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632223}
2 files changed