Compute cv_end_time with simpler logic (#6585)

Summary:
The refactored logic is easier to read.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6585

Test Plan: make check

Reviewed By: lth

Differential Revision: D20663225

Pulled By: cheng-chang

fbshipit-source-id: cfd28955cd03b0a71d9087085170875f6dd0be9e

utilities/transactions/transaction_lock_mgr.cc

@@ -348,13 +348,11 @@ Status TransactionLockMgr::AcquireWithTimeout(
     do {
       // Decide how long to wait
       int64_t cv_end_time = -1;
-
-      // Check if held lock's expiration time is sooner than our timeout
-      if (expire_time_hint > 0 &&
-          (timeout < 0 || (timeout > 0 && expire_time_hint < end_time))) {
-        // expiration time is sooner than our timeout
+      if (expire_time_hint > 0 && end_time > 0) {
+        cv_end_time = std::min(expire_time_hint, end_time);
+      } else if (expire_time_hint > 0) {
         cv_end_time = expire_time_hint;
-      } else if (timeout >= 0) {
+      } else if (end_time > 0) {
         cv_end_time = end_time;
       }