Schema compare tasks show default cancel context menu which does nothing

[udeeshagautam]

• Azure Data Studio Version:
  Version: 1.8.0-insider (system setup)
  Commit: d7df71c
  Date: 2019-05-31T14:51:26.886Z
  VS Code 1.34.0
  Electron: 3.1.8
  Chrome: 66.0.3359.181
  Node.js: 10.2.0
  V8: 6.6.346.32
  OS: Windows_NT x64 10.0.17763

Steps to Reproduce:

1. Schema comapre tasks Generate script and apply get an automatical context menu for cancel
2. It does nothitng but shows in UX as cancelled
3. This might get very confusing

We need to disable this cancel context menu option.

[udeeshagautam]

@kburtram do you think this qualifies for June?

[udeeshagautam]

Fixed by adding actual cancel operation on cancel