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This CL removes the no longer used host service script and updates
installer and other plist to use the new script.

Locally tested both fresh install and upgrade from M78 host and both
scenarios work.

Bug: 1013692, 10142116
Change-Id: If59e6a16fd1c3f86bfb76ddb5fbf850874d389a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1863735Reviewed-by: Lambros Lambrou <lambroslambrou@chromium.org>
Commit-Queue: Yuwei Huang <yuweih@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706203}