Use approx_time() instead of time(NULL) in some HS functions.

These were breaking our unittests.

src/or/hs_service.c

@@ -433,7 +433,7 @@ service_intro_point_new(const extend_info_t *ei, unsigned int is_legacy)
     if (BUG(intro_point_max_lifetime < intro_point_min_lifetime)) {
       goto err;
     }
-    ip->time_to_expire = time(NULL) +
+    ip->time_to_expire = approx_time() +
       crypto_rand_int_range(intro_point_min_lifetime,intro_point_max_lifetime);
   }
 

src/or/voting_schedule.c

@@ -168,7 +168,7 @@ voting_schedule_get_next_valid_after_time(void)
 
  done:
   if (need_to_recalculate_voting_schedule) {
-    voting_schedule_recalculate_timing(get_options(), now);
+    voting_schedule_recalculate_timing(get_options(), approx_time());
     voting_schedule.created_on_demand = 1;
   }