Fix missing expires_cursor check when existing defrag cycle (#14270)

Fix https://github.com/redis/redis/issues/13612
This bug was introduced by https://github.com/redis/redis/issues/11465

This PR added the incremental defragmentation for db->expires.
If the time for the defragmentation cycle has not arrived, it will exit
unless both cursor and expires_cursor are 0, meaning both keys and
expires have been fragmented.
However, the expires_cursor check has now been overlooked, which leads
to we will exit immediately even if the defragmentation doesn't reach
the end time, which will cause the efficiency of defragmentation to
become very low.

Note that this bug was already fixed in version
7.4(https://github.com/redis/redis/pull/13058)

src/defrag.c

@@ -1040,7 +1040,7 @@ void activeDefragCycle(void) {
                 server.stat_active_defrag_hits - prev_defragged > 512 ||
                 server.stat_active_defrag_scanned - prev_scanned > 64)
             {
-                if (!cursor || ustime() > endtime) {
+                if (!(cursor || expires_cursor) || ustime() > endtime) {
                     quit = 1;
                     break;
                 }