e2e/runtime/txsource: Allow one straggler, reduce timeouts

When long node restarts are enabled (e.g., nodes can be stopped for 10 min) it
can happen that the backup worker is stopped together with one of the primary
workers. Since we only have a single backup this will prevent discrepancy
resolution and cause rounds to always fail.

go/oasis-test-runner/scenario/e2e/runtime/txsource.go

@@ -437,10 +437,13 @@ func (sc *txSourceImpl) Fixture() (*oasis.NetworkFixture, error) {
 		// One executor can be offline.
 		f.Runtimes[1].Executor.GroupSize--
 		f.Runtimes[1].Executor.MinPoolSize--
+		// Allow one straggler to handle the case where the backup and primary worker are offline
+		// at the same time.
+		f.Runtimes[1].Executor.AllowedStragglers = 1
 
 		// Lower proposer and round timeouts as nodes are expected to go offline for longer time.
-		f.Runtimes[1].TxnScheduler.ProposerTimeout = 5
-		f.Runtimes[1].Executor.RoundTimeout = 15
+		f.Runtimes[1].TxnScheduler.ProposerTimeout = 4
+		f.Runtimes[1].Executor.RoundTimeout = 10
 	}
 
 	if sc.nodeRestartInterval > 0 || sc.nodeLongRestartInterval > 0 {