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Current Arc package sync implemetation does not support stop sync and re-enable
sync without rebooting. So user control of arc package sync is not achievable.
This patch re-implement sync stop and enable proper user control of arc package
sync using apps checkbox in advanced sync settings.

BUG= http://b/31034323, http://b/30640291, http://b/30980543
TEST=Pass sync integration test.
TEST=Manual test1. Turn on apps sync settings. Enable Arc and install package.
Nuke Arc then enable arc. Package restored.
TEST=Manual test2. Turn on apps sync settings. Enable Arc and install package.
Turn off apps sync settings and then nuke Arc. Then enable arc. Package not
restored. Then turn on apps sync settings. Package restored.

Review-Url: https://codereview.chromium.org/2277593002
Cr-Commit-Position: refs/heads/master@{#414277}