(bug 41342) jquery.suggestions: Call cancel before fetching.

(bug 41342) jquery.suggestions: Call cancel before fetching.

This caused race conditions in the calling code, if it used AJAX
and they completed in different order than they were started.

For example in mediawiki.searchSuggest, when one slowly types
"wikipedia", 9 requests get sent (suggestions for "w", "wi",
"wik", etc.), but they might not necessarily arrive in the same
order, especially on slow (e.g. mobile) connections.

Then you get the race condition effect - suggestions for
"wikipedia" flash briefly and then are replaced by suggestions for
"wik", even though the bolding is correct.

This commit fixes the issue by using a function that was already
present, that calls the callback as well as clearing the internal
timeout, which for some reason wasn't used in this code path.

Change-Id: I880a61e5e45a64bea6d679ed160c4be3da085dfa