Canceling Find All References while an existing operation is "confirming" references on an open file can cause the results to show "Cannot confirm reference"

[sean-mcmanus]

1. Find All References on something that takes a long time.
2. Find All References on something fast (i.e. local variable) while the previous operation is "confirming".

Another possible repro is to just to Cancel the operation while it's confirming results for an open file and then do the 2nd Find All References.

Bug: It shows the results for step 2 as "Cannot confirm reference" instead of confirmed references.

The problem was that the Cancel was killing the IntelliSense clients for open files when it shouldn't have.