roachtest: increase the concurrency for gracefuldraining

Previously the workload concurrency of 8 could cause spurious test
failures as the test would incorrectly count a single slow range as
causing too large of a dip. This isn't ideal behavior as we should have
more stable performance over time, but this is orthogonal to the goal of
this test. With a higher concurrency this test doesn't flake anymore.

Epic: none
Fixes: cockroachdb#106490

Release note: None

Author: Andrew Baptist

pkg/cmd/roachtest/tests/kv.go

@@ -558,7 +558,7 @@ func registerKVGracefulDraining(r registry.Registry) {
 			desiredRunDuration := 5 * time.Minute
 			m.Go(func(ctx context.Context) error {
 				cmd := fmt.Sprintf(
-					"./cockroach workload run kv --duration=%s --read-percent=0 --max-rate=%d {pgurl:1-%d}",
+					"./cockroach workload run kv --duration=%s --read-percent=0 --concurrency=100 --max-rate=%d {pgurl:1-%d}",
 					desiredRunDuration, specifiedQPS, nodes-1)
 				t.WorkerStatus(cmd)
 				defer func() {