Disable the "Sync Your Notes" button while "Syncing changes" status is displayed

[Softvision-MariusComan]

[Notes]:

• If the "Sync Your Notes" button is active and actionable while the "Syncing changes" status is displayed, then the behavior from issue Disable the "Sync Your Notes" button while "Saved at (hour)" status is displayed #479 will be reproducible again.

[Affected versions]:

• Firefox 58.0.2 and up

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Have a Firefox profile with the latest version of the "Firefox Notes" add-on (3.0.0rc2) installed.
• You are logged into "Firefox Notes".

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites.
2. Write something in the sidebar.
3. Observe the "Sync Your Notes" button while the "Syncing changes" status is displayed.

[Expected result]:

• The "Sync Your Notes" button is inactive.

[Actual result]:

• The "Sync Your Notes" button is active and actionable.

[Additional Notes]:

• Attached a screen recording of the issue:
  

[vladikoff]

@sebastienbarbier is this easy to fix with React?