send UPDATE instead of CREATE for sites

[diracdeltas]

see brave/sync#111 (comment)

fix brave/sync#111

test plan:

1. create some folders and bookmarks in pyramid 0
2. create some folders and bookmarks in pyramid 1
3. create sync group in pyramid 0 and join it on pyramid 1
4. on pyramid 0, bookmark a new site. wait for it to sync over.
5. drag-and-drop the new bookmark into a folder. verify that this is synced.
6. right-click to edit an existing bookmark and change the parent folder. verify this is synced.

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.

Test Plan:

Reviewer Checklist:

Tests

• Adequate test coverage exists to prevent regressions
• Tests should be independent and work correctly when run individually or as a suite ref
• New files have MPL2 license header

[alexwykoff]

left-to-right order on initial sync didn't appear to propagate
(top os x, bottom linux)

otherwise the rest of the steps seem fine. certainly fixes the primary case of managing folder structure and updating appropriately

[ayumi]

sweet, test plan works and tests pass (npm run test -- --grep='^Syncing and clearing' is intermittent but i think it's in master as well.)

🌵

[diracdeltas]

@alexwykoff as mentioned in slack and during the triage, order is not preserved during sync yet

[SergeyZhukovsky]

++

[alexwykoff]

@diracdeltas correct, just wanted to list it as observed so we don't need to re-test to see if we got a 2-for-1 😸