This is a check used in webserve.py getManualSearchStatus(), to get the ...

...current running queuitem, if it is a manual or failed/retry search. If so, the frontend will report the matching episode as in status "searching".

The function is_manualsearch_in_progress() is introduced for this purpose and only reference in webserve.py.
Previously when a daily search is running, and a manual search is queued behind it, it will wrongly give back that the manual search is running, this could result in unexpected behavior.