Certificate generation failure on Clone leads to warning

When a site Clone task is running, certificate generation is attempted 4 times:

1. The source site: No problems.
2. The destination site: Failure warning issued as site has not been configured yet.
3. The destination site: No problems; Initial certificate is generated.
4. The source site: No problems.

This seems a bit wasteful. Only the third step needs to run, but not really, as this will happen on the forthcoming destination site's Verify task.

In any case, we should somehow block the second step from running, as it's causing an unnecessary warning.