Update jquery interval check to support void javascript execution.

After deploying the last changes, a couple issues were found.

1. javascript functions with `void` return would not properly execute within the async callback (`Execute` vs. `ExecuteAndGet`).
2. The 'check for jquery' properties were not being populated across object creation, such as when `TryInvokeMember` is called.

Once this is approved I will create a PR for the master branch.
I see these last three lines are getting duplicated. Can you extract it to a method?