Rename {dual,triple}_timestamp_get to {dual,triple}_timestamp_now

Those functions take a pointer to a timestamp and return a timestamp pointer,
so the reader would be justified to think that those are just getters. Rename
them to avoid confusion.

src/systemctl/systemctl-list-units.c

@@ -769,7 +769,7 @@ int verb_list_timers(int argc, char *argv[], void *userdata) {
                 if (n < 0)
                         return n;
 
-                dual_timestamp_get(&nw);
+                dual_timestamp_now(&nw);
 
                 FOREACH_ARRAY(u, unit_infos, n) {
                         r = add_timer_info(bus, u, &nw, &timers, &n_timers);

src/systemctl/systemctl-show.c

@@ -484,7 +484,7 @@ static void print_status_info(
                 dual_timestamp nw, next = {i->next_elapse_real, i->next_elapse_monotonic};
                 usec_t next_elapse;
 
-                dual_timestamp_get(&nw);
+                dual_timestamp_now(&nw);
                 next_elapse = calc_next_elapse(&nw, &next);
 
                 if (timestamp_is_set(next_elapse))