Accept 'OK' status results from search engine

Accept 'OK' status results from search engine

Historically code that talks to the SearchEngine has been treating
anything other than a 'Good' result, such as results but with a warning
(perhaps the query timed out and only gave partial results) as a
complete failure. Adjust the handling to report results from an 'OK'
status response while attaching any warnings to the api response, or
in a notiable red box on Special:Search.

Bug: T134157
Change-Id: Ic5e0db727790f4fd189caa54ea5f01672d6a8ea4