Restore skipping update via OOBE configuration

Existing approach did not work on official builds (because skipping
update is not supported on them).

Test: OobeConfigurationEnrollmentTest.*, with check that removing
"updateSkipNonCritical" from sample configuration breaks tests.

Bug: 854101
Change-Id: Ic8e598bec9297f5f6e3333abb42a5b2b0018df78
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1619810
Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Denis Kuznetsov <antrim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661369}
5 files changed