core: don't restart on SIGHUP
core: don't restart on SIGHUP

18ff98992692 ("Respond to SIGHUP") adds a restart handler for SIGHUP, but
that doesn't really make sense. SIGHUP means the session has died, so
there's no use in restarting.

This breaks stuff like:

   loginctrl terminate-session $XDG_SESSION_ID

Instead, let's just gracefully stop qtile.

Fixes #2256

Signed-off-by: Tycho Andersen <6b523322678240882acbb4da5312a12d8cd0082d@tycho.pizza>

qtile/qtile,qtile/qtile,ramnes/qtile,ramnes/qtile