Bookmarks are synced when not connected to sync chain

Found when verifying https://github.com/brave/brave-browser/issues/3225

Steps to Reproduce

1. Create sync chain brave-core device1
2. Connect to sync chain brave-core device2
3. Create bookmark on device1 and ensure it is synced to device2
4. Copy sync codes from device1
5. On device2 press Leave Sync Chain
6. Wait until both devices will get sync turned off
7. Try to sync brave-core device3 with sync codes from 4.

Actual result:

bookmark is synced, even though joining sync chain fails.

On device3:

Expected result:

bookmark is not synced.

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

device1: brave 0.61.38 on Windows 7 device2: brave 0.62.8 on Windows 7 device3: brave 0.61.38 on Ubuntu 17.10

Brave	0.61.38 Chromium: 73.0.3683.39 (Official Build) beta (64-bit)
Revision	cc53b0e12fcaf42e4bab8d6c23bd4fb7aae99f6c-refs/branch-heads/3683@{#413}
OS	Windows 7 Service Pack 1 Build 7601.24312

Related issues: https://github.com/brave/brave-browser/issues/2687

cc @brave/legacy_qa @AlexeyBarabash

[AlexeyBarabash]

@kjozwiak , yes, sorry, missed milestone 2nd time in row after merging. Done.

[bsclifton]

Removed from release-notes/include since impact to customer is the same as https://github.com/brave/brave-browser/issues/2687