[#15945] DocDB: Increase wait timeout in TestDeleteTable TSAN mode

Summary:
The method TestDeleteTable waits for master leader after restart.
But timeout (5s) does not use kTimeMultiplier, so sometimes test fails in TSAN because we don't have master leader after 5 seconds.

Fixed by using kTimeMultiplier for timeout.
Jira: DB-5357

Test Plan: ./yb_build.sh tsan -n 100 --cxx-test client_backup-txn-test --gtest_filter BackupTxnTest.DeleteTableWithMastersRestart -- -p 4

Reviewers: timur

Reviewed By: timur

Subscribers: ybase

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D40934

src/yb/client/backup-txn-test.cc

@@ -549,7 +549,7 @@ void BackupTxnTest::TestDeleteTable(bool restart_masters) {
 
   if (restart_masters) {
     ASSERT_OK(StartAllMasters(cluster_.get()));
-    ASSERT_OK(WaitUntilMasterHasLeader(cluster_.get(), 5s));
+    ASSERT_OK(WaitUntilMasterHasLeader(cluster_.get(), 5s * kTimeMultiplier));
   }
 
   ASSERT_OK(snapshot_util_->WaitSnapshotInState(snapshot_id, SysSnapshotEntryPB::FAILED,