Autocomplete debounce-delay is broken with long-running requests

[mryellow]

With the request not responding before the delay timer it waits for them to finish and then sends more requests.

Steps to duplicate:

• Type 3 characters.
• 1 request is sent and waits for a response
• Response arrives
• Delay is triggered
• Another request is sent
• Response arrives
• Delay is triggered
• Another request is sent

Expected results:

• Type 3 characters
• 1 request is sent
• If further characters are typed when this is pending, the request should be cancelled

debounce-delay functioning should be not be dependant on response times.

[mryellow]

I believe this long-running request suffered the same issue but was misunderstood. #418

[mryellow]

This comment talks about Q promises being understood but normal Promises failing. Perhaps ties in here.

#135 (comment)