[3.13] gh-109413: Fix libregrtest get_running() (GH-127153) (#127157)

gh-109413: Fix libregrtest get_running() (GH-127153)

Skip threads which are not running.
(cherry picked from commit 0cb20177d667f0058f3d8d808abaf340e8345f04)

Co-authored-by: Victor Stinner <[email protected]>
1 file changed