Cache server connection is not checked when re-importing all assets

When choosing to re-import assets by downloading from the cache server, the client should also check that it can connect, not only that it's enabled.

Reproduce in any project:

1. In Project Settings, check that the Cache Server is Enabled and Download is Enabled.
2. Disconnect from the Cache Server (for example, by stopping the Accelerator service)
3. Right-click Project window.
4. Click Re-import All Assets.
5. Click Download from Cache Server

 

Expected: Re-import is cancelled as a connection cannot be established.

Actual: Re-import occurs without downloading from the cache server.