Revert "freebsd_network: Adjust callout_reset to drain not stop callouts."

This reverts commit 259f9a76d8.

This does not work with callouts that reschedule themselves, which is
something certain drivers indeed do.

src/libs/compat/freebsd_network/callout.cpp

@@ -176,7 +176,7 @@ callout_init_mtx(struct callout *c, struct mtx *mtx, int flags)
 int
 callout_reset(struct callout *c, int _ticks, void (*func)(void *), void *arg)
 {
-	int canceled = callout_drain(c);
+	int canceled = callout_stop(c);
 
 	MutexLocker locker(sLock);