emacs: Fix refresh of search results to leave cursor on current thread.

emacs: Fix refresh of search results to leave cursor on current thread.

This has been broken since the addition of support for streaming
search results to the emacs interface. With the old apparoach it was
easy to simply wait for all search results to land in the buffer and
then search for the desired line. With streaming results, we have to
save the target off to the side and allow the process filter and
sentinel functions to correctly respond when the target thread
appears.