Fix uninitialized nstime reading / updating on the stack in hpa.

In order for nstime_update to handle non-monotonic clocks, it requires the input
nstime to be initialized -- when reading for the first time, zero init has to be
done.  Otherwise random stack value may be seen as clocks and returned.

test/unit/hpa.c

@@ -349,7 +349,7 @@ defer_test_dehugify(void *ptr, size_t size) {
 
 static nstime_t defer_curtime;
 static void
-defer_test_curtime(nstime_t *r_time) {
+defer_test_curtime(nstime_t *r_time, bool first_reading) {
 	*r_time = defer_curtime;
 }