player: "subprocess" command should stop immediately in idle mode

The description of the "playback_only" field in the "subprocess" command
says "you can't start it outside of playback". This did not work
correctly: if the player was started in idle mode in the first place,
the subprocess was allowed to run even with playback_only=yes.

This is a bug, and this change fixes it. Add a test for this to
command-test.lua.

For #7025.

1 files changed, 2 insertions, 0 deletions

diff --git a/player/main.c b/player/main.c
index 4ab25a942c..bc6a3b1f97 100644
--- a/player/main.c
+++ b/player/main.c
@@ -319,6 +319,8 @@ struct MPContext *mp_create(void)
     if (verbose_env)
         mpctx->opts->verbose = atoi(verbose_env);
 
+    mp_cancel_trigger(mpctx->playback_abort);
+
     return mpctx;
 }