[8.2] Relax lastReservedThreads assertion in async mode to prevent test flakiness (#817)

Relax `lastReservedThreads` assertion in async mode to prevent test flakiness (#816)

relax lastReservedThreads test to avoid flakyness

(cherry picked from commit 31ba93e)

Co-authored-by: meiravgri <[email protected]>

Author: github-actions[bot]

tests/unit/test_svs_tiered.cpp

@@ -327,7 +327,7 @@ TYPED_TEST(SVSTieredIndexTest, TestDebugInfoThreadCount) {
     // Verify: numThreads unchanged, lastReservedThreads reflects actual availability
     backendIndexInfo = tiered_index->GetBackendIndex()->debugInfo();
     ASSERT_EQ(backendIndexInfo.svsInfo.numThreads, num_threads);
-    ASSERT_EQ(backendIndexInfo.svsInfo.lastReservedThreads, num_threads - 1);
+    ASSERT_LE(backendIndexInfo.svsInfo.lastReservedThreads, num_threads - 1);
 
     // Release occupied thread and trigger another background indexing
     thread_wait = false;
@@ -341,7 +341,7 @@ TYPED_TEST(SVSTieredIndexTest, TestDebugInfoThreadCount) {
     // Verify: numThreads unchanged, lastReservedThreads reflects we used all configured threads
     backendIndexInfo = tiered_index->GetBackendIndex()->debugInfo();
     ASSERT_EQ(backendIndexInfo.svsInfo.numThreads, num_threads);
-    ASSERT_EQ(backendIndexInfo.svsInfo.lastReservedThreads, num_threads);
+    ASSERT_LE(backendIndexInfo.svsInfo.lastReservedThreads, num_threads);
 }
 
 TYPED_TEST(SVSTieredIndexTest, TestDebugInfoThreadCountWriteInPlace) {