When setting a search, do a redisplay immediately

When setting a search, do a redisplay immediately

Commit 94bd6f17180f0a8cbdbf2a66a47469fce601a9e1 introduced a trick
where we only do the heavy lifting for "redisplay" when we're mapped.

However, the search system wants to get the count of matched items,
and control the visibility of the display based on that.  This introduces
a circularity; avoid it by forcing the search to do a redisplay.

In the future we should avoid this by separating out the "get matched
things for search" from "display list of things".

https://bugzilla.gnome.org/show_bug.cgi?id=600890