mapi_lib: reorder time checks in props_to_defer_interval

``if (*send_time < submit_time)`` logically implies
``if (nttime_to_unix(*send_time) < nttime_to_unix(submit_time))``, i.e.
``if (nttime_to_unix(*send_time) < nttime_to_unix(unix_to_nttime(cur_time))``, i.e.
``if (nttime_to_unix(*send_time) < cur_time``. But because the
time conversion functions have recently gained clamping, these conditions no
longer hold. Reorder the is-less-than test after time conversions to nudge
cov-scan.

CID 1596023: (#1 of 1): Overflowed return value (INTEGER_OVERFLOW)
5. return_overflow: rop_util_nttime_to_unix(*send_time) - cur_time,
which might have overflowed, is returned from the function.

Fixes: gromox-2.44-52-g438424e5f

Author: jengelh

lib/mapi/rop_util.cpp

@@ -248,15 +248,18 @@ XID::XID(GUID g, eid_t change_num) : guid(g), size(22)
 
 namespace gromox {
 
+/**
+ * Return number of seconds of how long to hold/defer a message.
+ */
 uint32_t props_to_defer_interval(const TPROPVAL_ARRAY &pv)
 {
 	auto cur_time = time(nullptr);
-	auto submit_time = rop_util_unix_to_nttime(cur_time);
 	auto send_time = pv.get<const uint64_t>(PR_DEFERRED_SEND_TIME);
 	if (send_time != nullptr) {
-		if (*send_time < submit_time)
+		auto ut_send_time = rop_util_nttime_to_unix(*send_time);
+		if (ut_send_time < cur_time)
 			return 0;
-		return rop_util_nttime_to_unix(*send_time) - cur_time;
+		return ut_send_time - cur_time;
 	}
 	auto num = pv.get<const uint32_t>(PR_DEFERRED_SEND_NUMBER);
 	if (num == nullptr)